Fix an interactive conflict resolution problem triggered by r1477876.

* subversion/svn/conflict-callbacks.c
  (conflict_func_interactive): Don't assume it's a text conflict
    whenever the node kind is 'file', as that could be a property
    conflict, so check that the conflict kind is 'text'.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1479605 13f79535-47bb-0310-9956-ffa450edef68