Allow getFileStats for non NFS ISO domains

getFileStats only allowed file stats to be gathered from NFS ISO domains.
We currently support ISO domains on any file storage domain so the check
was corrected.

Bug-Url: https://bugzilla.redhat.com/1075172
Change-Id: I7107d20b1b8b341086800bb35def895a70c4b4f0
Signed-off-by: Tal Nisan <tnisan@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/25627
Reviewed-on: http://gerrit.ovirt.org/25928
Reviewed-by: Yaniv Bronhaim <ybronhei@redhat.com>