xfstests: stop special casing nfs and udf

For historical reasons beyond my knowledge xfstests tries to abuse the
scratch device as test device for nfs and udf.  Because not all test
have inherited the right usage of the _setup_testdir and _cleanup_testdir
helpers this leads to lots of unessecary test failures.

Remove the special casing, which gets nfs down to a minimal number of
failures.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Sugned-off-by: Dave Chinner <david@fromorbit.com>

tests/generic/123

@@ -35,10 +35,9 @@ trap "_cleanup; exit \$status" 0 1 2 3 15
 
 _cleanup()
 {
-    cd $testdir
+    cd $TEST_DIR
     rm -rf $my_test_subdir
     cd /
-    _cleanup_testdir
 }
 
 # get standard environment, filters and checks
@@ -51,8 +50,7 @@ _supported_os Linux IRIX
 
 _require_user
 
-_setup_testdir
-my_test_subdir=$testdir/123subdir
+my_test_subdir=$TEST_DIR/123subdir
 
 # create subdir with required permissions
 mkdir -m 755 $my_test_subdir