T5594: vrrp: extend function is_ipv6_tentative

[nicolas-fort]

Change Summary

Backport fix #2281 to equuleus

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://vyos.dev/T5594
• T5594: vrrp: extend function is_ipv6_tentative #2281

Component(s) name

vrrp

Proposed changes

Backport fix for #2281

How to test

Smoketest:

root@vyos-133:/usr/libexec/vyos/tests/smoke/cli# ./test_ha_vrrp.py 
test_01_default_values (__main__.TestVRRP) ... ok
test_02_simple_options (__main__.TestVRRP) ... ok
test_03_sync_group (__main__.TestVRRP) ... ok
test_04_exclude_vrrp_interface (__main__.TestVRRP) ... ok

----------------------------------------------------------------------
Ran 4 tests in 11.695s

Config

vyos@vyos-133:~$ show ver | grep Ver
Version:          VyOS 1.3.3
vyos@vyos-133:~$ show config comm | grep "eth2\|vrrp"
set high-availability vrrp group 10 hello-source-address 'fe80::1'
set high-availability vrrp group 10 interface 'eth2'
set high-availability vrrp group 10 virtual-address 2001:db8::1/64
set high-availability vrrp group 10 vrid '10'
set interfaces ethernet eth2 address 'fe80::1/64'
set interfaces ethernet eth2 hw-id '50:00:00:04:00:02'
vyos@vyos-133:~$ show vrrp
  Name  Interface      VRID  State      Priority  Last Transition
------  -----------  ------  -------  ----------  -----------------
    10  eth2             10  MASTER          100  21m34s
vyos@vyos-133:~$ show int
Codes: S - State, L - Link, u - Up, D - Down, A - Admin Down
Interface        IP Address                        S/L  Description
---------        ----------                        ---  -----------
eth0             192.168.0.198/24                  u/u  
eth1             -                                 u/u  
eth2             2001:db8::1/64                    u/u  
eth3             -                                 u/u  
lo               127.0.0.1/8                       u/u  
                 ::1/128                                

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