Delay mux/sflow/snmp timer after interface-config service (#14506)

Why I did it
All these 3 services started after swss service, which used to start after interface-config service. But #13084 remove the time constraints for swss.

After that, these 3 services has the chance of start earlier when the inteface-config service is restarting the networking service, which could cause db connect request to fail.

How I did it
Delay mux/sflow/snmp timer after the interface-config service.

How to verify it
PR test.
Config reload can repro the issue in 1-3 retries. With this change. config reload run 30+ iterations without hitting the issue.

Signed-off-by: Ying Xie <[email protected]>

Author: yxieca

files/build_templates/mux.service.j2

@@ -1,7 +1,7 @@
 [Unit]
 Description=MUX Cable Container
 Requires=database.service updategraph.service swss.service
-After=swss.service
+After=swss.service interfaces-config.service
 BindsTo=sonic.target
 After=sonic.target
 StartLimitIntervalSec=1200

files/build_templates/sflow.service.j2

@@ -1,7 +1,7 @@
 [Unit]
 Description=sFlow container
 Requisite=swss.service
-After=swss.service syncd.service hostcfgd.service
+After=swss.service syncd.service hostcfgd.service interfaces-config.service
 BindsTo=sonic.target
 After=sonic.target
 Before=ntp-config.service

files/build_templates/snmp.timer

@@ -1,7 +1,7 @@
 [Unit]
 Description=Delays snmp container until SONiC has started
 PartOf=snmp.service
-After=swss.service
+After=swss.service interfaces-config.service
 
 [Timer]
 OnUnitActiveSec=0 sec