fstests: remove tmp files properly

Some tests and common helpers don't properly clean up tmp files and
leave them behind in /tmp dir, and these tmp files are accumulating
over time.

Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>

common/xfs

@@ -82,7 +82,7 @@ _scratch_mkfs_xfs()
 	local mkfs_cmd="`_scratch_mkfs_xfs_opts`"
 	local mkfs_filter="sed -e '/less than device physical sector/d' \
 			       -e '/switching to logical sector/d'"
-	local tmp=`mktemp`
+	local tmp=`mktemp -u`
 	local mkfs_status
 
 	_scratch_do_mkfs "$mkfs_cmd" "$mkfs_filter" $* 2>$tmp.mkfserr 1>$tmp.mkfsstd
@@ -104,7 +104,7 @@ _scratch_mkfs_xfs()
 	# output mkfs stdout and stderr
 	cat $tmp.mkfsstd
 	cat $tmp.mkfserr >&2
-	rm -f $tmp*
+	rm -f $tmp.mkfserr $tmp.mkfsstd
 
 	return $mkfs_status
 }