Merge r1502901 from trunk:

 * r1502901
   Make ra_serf sessions reusable after a log callback uses the
   SVN_ERR_CEASE_INVOCATION error.
   Justification:
     Without this patch a new session would be required for each of these
     usages.
     Required by the r1468980 group.
   Notes:
     Resets the connection used by ra_serf to avoid having to read all data,
     which is mostly the same behavior as not re-using the ra session.
   Votes:
     +1: rhuijben, stefan2, breser


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.8.x@1516002 13f79535-47bb-0310-9956-ffa450edef68
Merge r1502901 from trunk:

 * r1502901
   Make ra_serf sessions reusable after a log callback uses the
   SVN_ERR_CEASE_INVOCATION error.
   Justification:
     Without this patch a new session would be required for each of these
     usages.
     Required by the r1468980 group.
   Notes:
     Resets the connection used by ra_serf to avoid having to read all data,
     which is mostly the same behavior as not re-using the ra session.
   Votes:
     +1: rhuijben, stefan2, breser


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.8.x@1516004 13f79535-47bb-0310-9956-ffa450edef68