Make svnserve behave deterministically in case there is an error either
during opening the repo (incl auth) or normal command processing.

Without that, we are likely to segfault upon auth errors etc.

* subversion/svnserve/serve.c
  (serve_interruptable): Even in case of an error, make sure the
                         *TERMINATE_P receives a defined value such
                         that the caller knows whether to continue
                         using this connection.  Terminate when repo
                         access failed.

Found by: philip


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1570890 13f79535-47bb-0310-9956-ffa450edef68