[PATCH] xfstests: check if the scratch dev pool is mounted in _require_scratch

[Zach Brown]

> $SCRATCH_DEV, so anybody who wants to just use the scratch mnt with the scratch
> dev will fail to work because we never unmount the scratch mount.

Yeah, this is annoying.

> Fix this by
> checking to see if the scratch dev pool is mounted at scratch mnt and unmount it
> so we can run our test.  This fixes the issue I was seeing by running

But this fix seems bonkers.  Can we have _scratch_unmount unmount the
mountpoint instead of the device?  That's what Eric suggested when I
whined about this a while ago.

- z

index fe6bbfc..481486a 100644
--- a/common/rc
+++ b/common/rc
@@ -280,7 +280,7 @@ _scratch_mount()
 
 _scratch_unmount()
 {
-    $UMOUNT_PROG $SCRATCH_DEV
+    $UMOUNT_PROG $SCRATCH_MNT
 }
 
 _scratch_remount()