generic/490: fix cleanup function

generic/490 fails because cleanup tries to delete . and .. since $tmp
is left unset, and so "rm -f $tmp.*" does nothing useful. Instead
define $tmp and delete temp files created by seek_sanity_test.

[Eryu: define $tmp and remove $tmp.* too on cleanup]

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>

tests/generic/490

@@ -29,6 +29,7 @@ seqres=$RESULT_DIR/$seq
 echo "QA output created by $seq"
 
 here=`pwd`
+tmp=/tmp/$$
 status=1	# failure is the default!
 trap "_cleanup; exit \$status" 0 1 2 3 15
 
@@ -50,6 +51,7 @@ _cleanup()
 {
 	cd /
 	rm -f $tmp.*
+	rm -f $base_test_file*
 }
 
 $here/src/seek_sanity_test -s 19 -e 20 $base_test_file > $seqres.full 2>&1 ||