xfs: wrap xfs_db calls to the test device

Create a _test_xfs_db analogue to _scratch_xfs_db so that we can
encapsulate whatever strange test fs options were fed to us by the test
runner.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Zorro Lang <zlang@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>

common/xfs

@@ -218,6 +218,19 @@ _scratch_xfs_db()
 	$XFS_DB_PROG "$@" $(_scratch_xfs_db_options)
 }
 
+_test_xfs_db_options()
+{
+	TEST_OPTIONS=""
+	[ "$USE_EXTERNAL" = yes -a ! -z "$TEST_LOGDEV" ] && \
+		TEST_OPTIONS="-l$TEST_LOGDEV"
+	echo $TEST_OPTIONS $* $TEST_DEV
+}
+
+_test_xfs_db()
+{
+	$XFS_DB_PROG "$@" $(_test_xfs_db_options)
+}
+
 _scratch_xfs_admin()
 {
 	local options=("$SCRATCH_DEV")