[show] Add command 'show runningconfig ntp' (sonic-net#620)

Author: tsvanduyn

doc/Command-Reference.md

@@ -3010,7 +3010,11 @@ This command displays the running configuration of the ntp module.
 
 - Example:
   ```
-  admin@sonic:~$ show runningconfiguration ntp
+  admin@str-s6000-acs-11:~$ show runningconfiguration ntp
+  NTP Servers
+  -------------
+  1.1.1.1
+  2.2.2.2
   ```
 
 **show runningconfiguration syslog**
@@ -3023,7 +3027,7 @@ This command displays the running configuration of the syslog module.
 
 - Example:
   ```
-  admin@str-s6000-acs-11:~$ show run syslog 
+  admin@str-s6000-acs-11:~$ show runningconfiguration syslog 
   Syslog Servers
   ----------------
   4.4.4.4

show/main.py

@@ -1476,8 +1476,16 @@ def snmp(server, verbose):
 @click.option('--verbose', is_flag=True, help="Enable verbose output")
 def ntp(verbose):
     """Show NTP running configuration"""
-    cmd = "cat /etc/ntp.conf"
-    run_command(cmd, display_cmd=verbose)
+    ntp_servers = []
+    ntp_dict = {}
+    with open("/etc/ntp.conf") as ntp_file:
+        data = ntp_file.readlines()
+    for line in data:
+        if line.startswith("server "):
+            ntp_server = line.split(" ")[1]
+            ntp_servers.append(ntp_server)
+    ntp_dict['NTP Servers'] = ntp_servers
+    print tabulate(ntp_dict, headers=ntp_dict.keys(), tablefmt="simple", stralign='left', missingval="")
 
 
 # 'syslog' subcommand ("show runningconfiguration syslog")