Fix segfault in svnmucc.
Fix segfault in svnmucc.

* subversion/libsvn_client/mtcc.c
  (svn_client_mtcc_commit):  We explicitly destroy the MTCC pool and
                             have no knowledge about its relation to
                             SCRATCH_POOL.  Thus, we can't use the
                             for anything non-trivial.

git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@1555350 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion