Simplify error handling in 'svn merge'.  There's no need to run conflict
resolution if the merge threw an error, except in the one case where the
error is 'conflicts were raised'.

* subversion/svn/merge-cmd.c
  (svn_cl__merge): Change error handling as above.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1446332 13f79535-47bb-0310-9956-ffa450edef68