There are a few scenarios where init_active_labels() can return without
registering deactivate_labels() to run when the region is disabled. In
particular label error injection creates scenarios where a DIMM is
disabled, but labels on other DIMMs in the region become activated.

Arrange for init_active_labels() to always register deactivate_labels().
Reported-by: NKrzysztof Kensicki <krzysztof.kensicki@intel.com>
Cc: <stable@vger.kernel.org>
Fixes: bf9bccc1 ("libnvdimm: pmem label sets and namespace instantiation.")
Reviewed-by: NJeff Moyer <jmoyer@redhat.com>
Link: https://lore.kernel.org/r/162766356450.3223041.1183118139023841447.stgit@dwillia2-desk3.amr.corp.intel.comSigned-off-by: NDan Williams <dan.j.williams@intel.com>