networkd: Consider linkLocalAddressing state while configuring ndisc. (#7012)

If linkLocalAddressing is disabled in for the interface still then
we look for ndisc configured or not in link_check_ready.

Link local is used automatic address configuration and neighbor discovery protocol.
If link local is disabled we should not configure ndisc.

Fixes #2713, #6441, #5841.

(cherry picked from commit 702c979f)
(cherry picked from commit 610f5ddb)