bluetooth: mesh: remove persisted psa key if mesh does not own it

Commit adds destruction of the persisted in PSA ITS key if
mesh does not own it (zero bit in the bitmap of persisted keys).

This is not standard mesh behavior, but might happen
if something happens between removing key data in mesh and
in the crypto library (for example power off in bettwen).

Previously, mesh wasn't able to import key with gotten stuck
key id. The current fix reproduces more robust behavior.

Signed-off-by: Aleksandr Khromykh <aleksandr.khromykh@nordicsemi.no>