fileSD: remove reference to the removed safeUnlink

the method safeUnlink was replaced by rmFile
changed the file to use the new method

Change-Id: I5e6d632d6b1dcdbffa48158065921b3313a0b96a
Signed-off-by: Ohad Basan <obasan@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/17173
Reviewed-by: Dan Kenigsberg <danken@redhat.com>
Reviewed-by: Yeela Kaplan <ykaplan@redhat.com>