ifconfig: T2241: fix section _basename vlan stripping
ifconfig: T2241: fix section _basename vlan stripping

Previously the function returned the correct basename only for vif interfaces
as it stopped at the 2nd dot. If we had a vif-s vif-c interface 'eth0.1.2' it
would return 'eth0.'. It is now fixed to strip both vif-s and vif-c if
'vlan=True' (default).

vyos/vyos-1x,vyos/vyos-1x,vyos/vyos-1x,vyos/vyos-1x