Ticket #47359 - new ldap connections can block ldaps and ldapi connections

https://fedorahosted.org/389/ticket/47359
Reviewed by: lkrispen, nhosoi (Thanks!)
Branch: 389-ds-base-1.3.1
Fix Description: description
In the polling thread, first process all of the new connection requests from
the listening sockets, then process any new operation read requests
The listener_idxs keeps track of the index of the active listeners in the
poll fd array, and keeps a pointer to the listenfd object for that
listener.  This allows us to very quickly scan through the poll fd array
and find the ready listeners.  The work of scanning through the array
and handling the new connection requests has been moved to a new function
handle_listeners().
Platforms tested: RHEL6 x86_64
Flag Day: no
Doc impact: no
(cherry picked from commit 115ab1d9a3f026e8523b91bf62245a25454a3e8a)
(cherry picked from commit 24b751cc724468a7bce5f86848a82e4b03e24a3c)
Ticket 580 - Wrong error code return when using EXTERNAL SASL and no client certificate

Bug Description:  When doing a SASL EXTERNAL bind, and no client certificate is provided,
                  the bind succeeds(as anonymous).  However, the bind should fail with
                  an error 48.

Fix Description:  Check for the missing client certificate and return the appropriate
                  error.

https://fedorahosted.org/389/ticket/580

Reviewed by: Noriko(Thanks!)
(cherry picked from commit 2a81336e582c68fe0326a76a2f156b469688cc9b)