Revert "Add support for generating interface configuration in /etc/network/interfaces for multiple management interfaces (#11204)" (#11241)

This reverts commit 90a849e.

#### Why I did it
The interfaces unit test did not cover some of the conditions in interfaces.j2 that was changed in #11204.  Therefore reverting the change and add the tests before making the change to interfaces.j2.

#### How I did it
Git revert.

#### How to verify it

#### Which release branch to backport (provide reason below if selected)


- [ ] 201811
- [ ] 201911
- [ ] 202006
- [ ] 202012
- [ ] 202106
- [ ] 202111
- [ ] 202205

#### Description for the changelog

#### Link to config_db schema for YANG module changes

#### A picture of a cute animal (not mandatory but encouraged)

Author: geogchen

files/image_config/interfaces/interfaces.j2

@@ -30,27 +30,19 @@ iface lo inet loopback
 {% block mgmt_interface %}
 
 # The management network interface
-{% if MGMT_INTERFACE %}
-{% for (name, prefix) in MGMT_INTERFACE|pfx_filter|unique(attribute=0) %}
-auto {{ name }}
-{% endfor %}
-{% endif %}
+auto eth0
 {% if (ZTP_DHCP_DISABLED is not defined) and (ZTP is defined) and (ZTP['mode'] is defined and ZTP['mode']['profile'] == 'active') %}
 
 
 # ZTP out-of-band interface
-{% if MGMT_INTERFACE %}
-{% for (name, prefix) in MGMT_INTERFACE|pfx_filter|unique(attribute=0) %}
-allow-hotplug {{ name }}
+allow-hotplug eth0
 {% if ZTP['mode']['ipv4'] == 'true' %}
-iface {{ name }} inet dhcp
+iface eth0 inet dhcp
 {% endif %}
 {% if ZTP['mode']['ipv6'] == 'true' %}
-iface {{ name }} inet6 dhcp
-    up sysctl net.ipv6.conf.{{ name }}.accept_ra=1
-    down sysctl net.ipv6.conf.{{ name }}.accept_ra=0
-{% endif %}
-{% endfor %}
+iface eth0 inet6 dhcp
+    up sysctl net.ipv6.conf.eth0.accept_ra=1
+    down sysctl net.ipv6.conf.eth0.accept_ra=0
 {% endif %}
 
 {% if ZTP['mode']['inband'] == 'true' %}
@@ -73,7 +65,7 @@ iface {{ port }} inet6 dhcp
 {% else %}
 {% if MGMT_INTERFACE %}
 {% for (name, prefix) in MGMT_INTERFACE|pfx_filter %}
-iface {{ name }} {{ 'inet' if prefix | ipv4 else 'inet6' }} static
+iface eth0 {{ 'inet' if prefix | ipv4 else 'inet6' }} static
     address {{ prefix | ip }}
     netmask {{ prefix | netmask if prefix | ipv4 else prefix | prefixlen }}
     network {{ prefix | network }}
@@ -85,15 +77,15 @@ iface {{ name }} {{ 'inet' if prefix | ipv4 else 'inet6' }} static
 {% endif %}
     ########## management network policy routing rules
     # management port up rules
-    up ip {{ '-4' if prefix | ipv4 else '-6' }} route add default via {{ MGMT_INTERFACE[(name, prefix)]['gwaddr'] }} dev {{ name }} table {{ vrf_table }} metric 201
-    up ip {{ '-4' if prefix | ipv4 else '-6' }} route add {{ prefix | network }}/{{ prefix | prefixlen }} dev {{ name }} table {{ vrf_table }}
+    up ip {{ '-4' if prefix | ipv4 else '-6' }} route add default via {{ MGMT_INTERFACE[(name, prefix)]['gwaddr'] }} dev eth0 table {{ vrf_table }} metric 201
+    up ip {{ '-4' if prefix | ipv4 else '-6' }} route add {{ prefix | network }}/{{ prefix | prefixlen }} dev eth0 table {{ vrf_table }}
     up ip {{ '-4' if prefix | ipv4 else '-6' }} rule add pref 32765 from {{ prefix | ip }}/{{ '32' if prefix | ipv4 else '128' }} table {{ vrf_table }}
 {% for route in MGMT_INTERFACE[(name, prefix)]['forced_mgmt_routes'] %}
     up ip rule add pref 32764 to {{ route }} table {{ vrf_table }}
 {% endfor %}
     # management port down rules
-    pre-down ip {{ '-4' if prefix | ipv4 else '-6' }} route delete default via {{ MGMT_INTERFACE[(name, prefix)]['gwaddr'] }} dev {{ name }} table {{ vrf_table }}
-    pre-down ip {{ '-4' if prefix | ipv4 else '-6' }} route delete {{ prefix | network }}/{{ prefix | prefixlen }} dev {{ name }} table {{ vrf_table }}
+    pre-down ip {{ '-4' if prefix | ipv4 else '-6' }} route delete default via {{ MGMT_INTERFACE[(name, prefix)]['gwaddr'] }} dev eth0 table {{ vrf_table }}
+    pre-down ip {{ '-4' if prefix | ipv4 else '-6' }} route delete {{ prefix | network }}/{{ prefix | prefixlen }} dev eth0 table {{ vrf_table }}
     pre-down ip {{ '-4' if prefix | ipv4 else '-6' }} rule delete pref 32765 from {{ prefix | ip }}/{{ '32' if prefix | ipv4 else '128' }} table {{ vrf_table }}
 {% for route in MGMT_INTERFACE[(name, prefix)]['forced_mgmt_routes'] %}
     pre-down ip rule delete pref 32764 to {{ route }} table {{ vrf_table }}

src/sonic-config-engine/minigraph.py

@@ -10,7 +10,6 @@
 from lxml import etree as ET
 from lxml.etree import QName
 
-from natsort import natsorted
 
 from portconfig import get_port_config
 from sonic_py_common.interface import backplane_prefix
@@ -1433,8 +1432,7 @@ def parse_xml(filename, platform=None, port_config_file=None, asic_name=None, hw
     results['MGMT_INTERFACE'] = {}
     mgmt_intf_count = 0
     mgmt_alias_reverse_mapping = {}
-    sorted_keys = natsorted(mgmt_intf.keys(), key=lambda x : x[0].lower())
-    for key in sorted_keys:
+    for key in mgmt_intf:
         alias = key[0]
         if alias in mgmt_alias_reverse_mapping:
             name = mgmt_alias_reverse_mapping[alias]