heimdal: fix endless loop for specific KDC error code

heimdal: fix endless loop for specific KDC error code

When sending a Kerberos request, if at least one of the available
KDCs repeatedly replies with an error response of
KRB5KDC_ERR_SVC_UNAVAILABLE, and all other KDCs, if there are any,
do not reply at all or cannot be contacted, then the code repeatedly
retries to send the request in an endless loop.

This is fixed in upstream (post 1.5 branch) heimdal but the code
there is vastly refactored, so this is an independent fix to the issue.

Signed-off-by: Uri Simchoni <urisimchoni@gmail.com>
Reviewed-by: Alexander Bokovoy <ab@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Wed Jun 17 02:34:31 CEST 2015 on sn-devel-104