Fix some tests I inadvertantly broke with r30455.
Fix some tests I inadvertantly broke with r30455.

* subversion/tests/cmdline/log_tests.py
  (merge_history_repos): Append '@HEAD' to the merge sources in
    various 'svn merge WC-PATH' invocations.

git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@870534 13f79535-47bb-0310-9956-ffa450edef68

wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion