Use separate locking directory for each of the tests, as they never share a

volume group, or physical devices for that matter. Hopefully fixes occasional
test errors due to locking failures. Patch by jstava.

test/test-utils.sh

@@ -170,6 +170,7 @@ prepare_lvmconf() {
   }
   global {
     library_dir = "$G_root_/lib"
+     locking_dir = "$G_root_/var/lock/lvm"
   }
 EOF
 }