common/dump: do not override test cleanup trap

Instead, call _cleanup_dump explicitly from a private _cleanup.
Remove the generic cleanup bits (rm $tmp.*) from _cleanup_dump.

The only xfs/dump test that had anything other than rm $tmp.* in
_cleanup in xfs/287, but that was _scratch_unmount, which is not
needed anyway.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>

tests/xfs/055

@@ -14,7 +14,14 @@ echo "QA output created by $seq"
 here=`pwd`
 tmp=/tmp/$$
 status=1	# failure is the default!
-trap "rm -f $tmp.*; exit \$status" 0 1 2 3 15
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+_cleanup()
+{
+	_cleanup_dump
+	cd /
+	rm -f $tmp.*
+}
 
 # get standard environment, filters and checks
 . ./common/rc