Remove some remains of pre Subversion 1.7 working copy test scenarios.

* subversion/tests/cmdline/svntest/deeptrees.py
  (deep_trees_after_leaf_del_no_ci,
   deep_trees_after_tree_del_no_ci): Assume that we use a single wc.db per
     working copy.
     
  (deep_trees_empty_dirs): Remove now unused variable.
   
* subversion/tests/cmdline/upgrade_tests.py
  (check_format): Assume single db.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1549805 13f79535-47bb-0310-9956-ffa450edef68