btrfs-progs: test: Add test image for btrfsck qgroup rescan detection

Fixed by commit 7c646c538e btrfs-progs: qgroup: Fix regression leads
to corrupted qgroup status.

Add minimal test image for that fix.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
[ minor cleanups in test.sh ]
Signed-off-by: David Sterba <dsterba@suse.com>

tests/fsck-tests/022-qgroup-rescan-halfway/test.sh

@@ -0,0 +1,19 @@
+#!/bin/bash
+# check whether btrfsck can detect running qgroup rescan
+
+source $TOP/tests/common
+
+check_prereq btrfs
+
+check_image() {
+	local image
+
+	image=$1
+	run_check_stdout $TOP/btrfs check "$image" 2>&1 | \
+		grep -q "Counts for qgroup id"
+	if [ $? -eq 0 ]; then
+		_fail "Btrfs check doesn't detect rescan correctly"
+	fi
+}
+
+check_all_images "."