Since we have qemuSecurity wrappers over
virSecurityManagerSetHostdevLabel and
virSecurityManagerRestoreHostdevLabel we ought to use them
instead of calling secdriver APIs directly.  Without those
wrappers the labelling won't be done in the correct namespace
and thus won't apply to the nodes seen by qemu itself.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>