dmu_recv_end_check: don't leak hold if dsl_destroy_snapshot_check_impl fails

The leak may happen if !drc_newfs && drc_force and there is an error
iterating through snapshots or any of snapshot checks fails.

See https://www.illumos.org/issues/5870
See https://reviews.csiden.org/r/206/

Reviewed by: mahrens (as mahrens@delphix.com)
MFC after: 15 days
Sponsored by: ClusterHQ