Make NEC Plugin keep error resources

NEC Plugin used to ignore OFC errors while deleting resources from OFC,
and it could leave some unused resources on OFC. If OFC generates id
which is in remained resources when creating new resource, it will fail.

This commit makes NEC Plugin keep logical resource when it failed to
delete resource from OFC not to leave orphan resource on OFC, and raise
exception to tell the user that the resouce status is Error.

NOTE: The user can retry deletion. If the resouce was successfully
deleted from OFC in retries, the logical resource will be deleted.

Fixes: bug #1206416
Change-Id: Ifea38dfe3fe8b18d7ae1cedf86a23008549250cc
Merge "Make NEC Plugin keep error resources"