[show] Moving some py imports inside specific cmds (#1202)

- Some py imports in show/main.py script are taking more time on arm cpu.
- modules - pkg_resources, netaddr are taking around 500ms causing delay for all show cmds.
- These modules are used by only specific cmds. So, I have included these imports only for the commands that are using them.

Signed-off-by: Sabareesh Kumar Anandan <sanandan@marvell.com>

show/main.py

@@ -1,5 +1,4 @@
 import json
-import netaddr
 import os
 import subprocess
 import sys
@@ -9,7 +8,6 @@
 import utilities_common.cli as clicommon
 import utilities_common.multi_asic as multi_asic_util
 from natsort import natsorted
-from pkg_resources import parse_version
 from sonic_py_common import device_info, multi_asic
 from swsssdk import ConfigDBConnector
 from swsscommon.swsscommon import SonicV2Connector
@@ -751,6 +749,7 @@ def get_if_master(iface):
 @ip.command()
 def interfaces():
     """Show interfaces IPv4 address"""
+    import netaddr
     header = ['Interface', 'Master', 'IPv4 address/mask', 'Admin/Oper', 'BGP Neighbor', 'Neighbor IP']
     data = []
     bgp_peer = get_bgp_peer()
@@ -1266,6 +1265,7 @@ def bgp(verbose):
 @click.option('--verbose', is_flag=True, help="Enable verbose output")
 def ntp(ctx, verbose):
     """Show NTP information"""
+    from pkg_resources import parse_version
     ntpstat_cmd = "ntpstat"
     ntpcmd = "ntpq -p -n"
     if is_mgmt_vrf_enabled(ctx) is True:

utilities_common/cli.py

@@ -6,7 +6,6 @@
 
 import click
 import json
-import netaddr
 
 from natsort import natsorted
 from sonic_py_common import multi_asic
@@ -191,6 +190,7 @@ def get_interface_naming_mode():
 
 def is_ipaddress(val):
     """ Validate if an entry is a valid IP """
+    import netaddr
     if not val:
         return False
     try: