Fix issue #4298 "'svn sw' with add on unversioned segfaults".

* subversion/libsvn_wc/conflicts.c
  (svn_wc__read_conflicts): Follow-up to r1432454, use the correct pool
   when allocating svn_wc_conflict_description2_t.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1436564 13f79535-47bb-0310-9956-ffa450edef68