isisd: clean ipv4/6 circuit config on destroy

isisd: clean ipv4/6 circuit config on destroy

when deleting an isis interface config with 'no [ip|ipv6] router isis'
we are destroying the isis yang container for that interface, but the
actual circuit struct is kept, and so are the flgs determining whether
that circuit is configured for ipv4 and/or ipv6. This caused issues
when removing and re-adding configuration, as the area counters for
ip circuits were not correctly updated and the topology was never
populated.

Signed-off-by: Emanuele Di Pascale <emanuele@voltanet.io>