ipsec prefix: T4275: Fix for prefix val_help of remote-access and s2s vpn

[srividya0208]

Change Summary

It accepts network as the input value but the completion help is showing
ip address in other section also(part of the previous commit)

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/T4275

Component(s) name

ipsec vpn

Proposed changes

Existing:

vyos@vyos# set vpn ipsec remote-access pool test prefix
Possible completions:
   <x.x.x.x>    Local IPv4 pool prefix
   <h:h:h:h:h:h:h:h>
                Local IPv6 pool prefix

vyos@vyos# set vpn ipsec remote-access pool test exclude
Possible completions:
   <x.x.x.x>    Local IPv4 pool prefix exclusion
   <h:h:h:h:h:h:h:h>
                Local IPv6 pool prefix exclusion
Remote prefix:

vyos@vyos# set vpn ipsec site-to-site peer 172.21.0.2 tunnel 0 remote prefix
Possible completions:
   <x.x.x.x>    Remote IPv4 prefix
   <h:h:h:h:h:h:h:h>
                Remote IPv6 prefix

Proposed:

vyos@vyos# set vpn ipsec site-to-site peer 172.21.0.2 tunnel 0 remote prefix
Possible completions:
   <x.x.x.x/x>    Remote IPv4 prefix
   <h:h:h:h:h:h:h:h/h>
                Remote IPv6 prefix

How to test

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