Prevent spurious failures in client-test 8 when CLEANUP isn't used.

* subversion/tests/libsvn_client/client-test.c
  (test_suggest_mergesources): Have to remove the wc before doing
    a checkout, otherwise you get an error on UUID mismatches.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1558946 13f79535-47bb-0310-9956-ffa450edef68