Make move-update bail-out when encountering a merge conflict.

* subversion/libsvn_wc/wc_db_update_move.c
  (mark_tree_conflict, get_tc_info): Ensure an existing tree-conflict
   is an update or switch operation.

* subversion/libsvn_wc/conflicts.c
  (resolve_conflict_on_node): Check the conflict operation earlier
   to avoid attempting move-update actions on merge conflicts.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1443948 13f79535-47bb-0310-9956-ffa450edef68