T4070: natv4: Add "any" for inbound-interface list

[srividya0208]

Change Summary

"any" was missing from the interface list which will be useful to indicate any
interface.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Code style update (formatting, renaming)
• Refactoring (no functional changes)
• Migration from an old Vyatta component to vyos-1x, please link to related PR inside obsoleted component
• Other (please describe):

Related Task(s)

• https://phabricator.vyos.net/Txxxx
  https://phabricator.vyos.net/T4070

Component(s) name

nat

Proposed changes

Added "any" option to reflect in the inbound-interface list

How to test

vyos@vyos# set nat destination rule 100 inbound-interface
Possible completions:
   <text>       Inbound interface of NAT traffic
   any
   eth0
   eth1
   eth2
   eth3
   lo

Checklist:

• I have read the CONTRIBUTING document
• I have linked this PR to one or more Phabricator Task(s)
• I have run the components SMOKETESTS if applicable
• My commit headlines contain a valid Task id
• My change requires a change to the documentation
• I have updated the documentation accordingly