core: ForceSelectSPM might fail

ForceSelectSPM is performing nothing in case that the current SPM can't
be stopped but its execution is always marked as succesful.
In case of failure an appropiate audit log should be displayed.

Change-Id: Ia1a32ec7b68c3643e28751d61ba070b4e4cc09ea
Bug-Url: https://bugzilla.redhat.com/1119852
Signed-off-by: Liron Aravot <laravot@redhat.com>