btrfs: add regression test for incremental send

Test for a btrfs incremental send issue where we end up sending a
wrong section of data from a file extent if the corresponding file
extent is compressed and the respective file extent item has a non
zero data offset.

Fixed by the following linux kernel btrfs patch:

   Btrfs: use right clone root offset for compressed extents

Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

common/rc

@@ -2207,6 +2207,11 @@ run_check()
 	"$@" >> $seqres.full 2>&1 || _fail "failed: '$@'"
 }
 
+_run_btrfs_util_prog()
+{
+	run_check $BTRFS_UTIL_PROG $*
+}
+
 init_rc()
 {
 	if [ "$iam" == new ]