Make fsfs implementation of svn_fs_commit_txn adhere to API promises.
Make fsfs implementation of svn_fs_commit_txn adhere to API promises.

* subversion/libsvn_fs_fs/tree.c
  (svn_fs_fs__commit_txn): If the commit fails then the *NEW_REV argument
  should be SVN_INVALID_REVNUM.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion