Partial revert "Disable slow tests for kmemleak"

Enable zpool_clear_001_pos, zpool_create_024_pos and inherit_001_pos. These
are no longer slow.

Also disable zfs_destroy_001_pos, zfs_allow_010_pos and snapused_004_pos,
as they fail very often.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Closes #5613

tests/zfs-tests/tests/functional/snapused/snapused_004_pos.ksh

@@ -51,6 +51,11 @@
 
 verify_runnable "both"
 
+# See issue: https://github.com/zfsonlinux/zfs/issues/5479
+if is_kmemleak; then
+	log_unsupported "Test case often fail when kmemleak is enabled"
+fi
+
 function cleanup
 {
 	log_must $ZFS destroy -rR $USEDTEST