Resolve an ugly regression introduced by the inherited property support.

An inaccessible switched location would make the update run against the
wrong target, producing a nice error instead of running an update.

* subversion/libsvn_client/client.h
  Document changed error behavior.

* subversion/libsvn_client/iprops.c
  (get_inheritable_props): New function, extracted from
    svn_client__get_inheritable_props.
  (svn_client__get_inheritable_props): Wrap get_inheritable_props to make
    sure this function never returns without trying to restore the ra session.

* subversion/libsvn_client/update.c
  (update_internal): Wrap svn_client__get_inheritable_props call with SVN_ERR()

* subversion/tests/cmdline/update_tests.py
  (update_removes_switched): Remove XFail marker. Expect the current behavior to
    show and verify that the problem identified in this patch is fixed.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1435684 13f79535-47bb-0310-9956-ffa450edef68