QA updates to enable simplified large filesystem testing

tools/auto-qa

@@ -216,6 +216,10 @@ _test_mkfs_xfs()
     [ "$USE_EXTERNAL" = yes -a ! -z "$TEST_LOGDEV" ] && \
         TEST_OPTIONS="$TEST_OPTIONS -llogdev=$TEST_LOGDEV"
     _sudo /sbin/mkfs.xfs -f $TEST_OPTIONS $MKFS_OPTIONS $* $TEST_DEV
+    mkfs_status=$?
+    [ "$USE_BIG_LOOPFS" = yes ] && \
+        _sudo $QADIR/tools/ag-wipe -c $TEST_DEV >/dev/null
+    return $mkfs_status
 }
 
 _test_mount()