isisd: log adj change when circuit goes down

isisd: log adj change when circuit goes down

if we shutdown an interface isisd will delete the adjacencies
on the corresponding circuit, but it will not log the change.
Fix it to make sure that each change is logged. Also specify
the level of the adjacency in the log message, while we are at it.

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