Fix a dormant pool usage bug that I introduced in r1149264 and
partially fixed in r1159672. The current callers were all safe.

* subversion/libsvn_client/repos_diff.c
  (get_file_from_ra): Allocate the checksum result in 'fb->pool', not in
    'scratch_pool'.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1480416 13f79535-47bb-0310-9956-ffa450edef68