Improve error handling during a 'replay' using Serf. 

The function svn_ra_serf__replay_range() doesn't return any error 
while running 'svnrdump dump -rN:M <URL-deleted-in-HEAD>'[Issue #4100]. 
It behaves as if the dump completed successfully.

* subversion/libsvn_ra_serf/replay.c
  (svn_ra_serf__replay_range): Handle the errors from server's response as
    well as any errors found while running the serf loop.

Patch by: Vijayaguru G <vijay{_AT_}collab.net>