common/rc: use _try_scratch_mount for scratch_remount

When call _scratch_remount for cifs , it always requires to input
password. This will make generic/306 generic/452 failed because
cifs remount failed.

Signed-off-by: Xiaoli Feng <xifeng@redhat.com>
Reviewed-and-tested-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>

common/rc

@@ -357,7 +357,7 @@ _scratch_remount()
     local opts="$1"
 
     if test -n "$opts"; then
-	mount -o "remount,$opts" $SCRATCH_MNT
+	_try_scratch_mount "-o remount,$opts"
     fi
 }
 

tests/overlay/035

@@ -55,7 +55,7 @@ mkdir -p $lowerdir1 $lowerdir2 $upperdir $workdir
 $MOUNT_PROG -t overlay -o"lowerdir=$lowerdir2:$lowerdir1" \
 			$OVL_BASE_SCRATCH_MNT $SCRATCH_MNT
 touch $SCRATCH_MNT/foo 2>&1 | _filter_scratch
-_scratch_remount rw 2>&1 | _filter_ro_mount
+$MOUNT_PROG -o remount,rw $SCRATCH_MNT 2>&1 | _filter_ro_mount
 $UMOUNT_PROG $SCRATCH_MNT
 
 # Make workdir immutable to prevent workdir re-create on mount