Trac Ticket #402 - nhashed#user#password in entry extension

Description: commit 091c749adcc53ef3332cab6d34b25dadcb69c696
had a logic flaw: entry_apply_mod_wsi checks whether modify
candidate attribute is to be stored in an entry extension or
not. If it is supposed to be in the entry extension, it removes
the attribute from the entry attribute list (e_attrs), and put
it into the entry extension. The steps have to be done under
any condition, but entry_apply_mod_wsi used to check if the
entry extension was configured properly and the attribute
existed in the extension, first.  If both were not satisfied,
the attribute was not removed from the attribute list.

This patch eliminated the check and the attribute to be stored
in the entry extension is always removed from the attribute
list in the entry.

Reviewed by Nathan (Thank you!!)

https://fedorahosted.org/389/ticket/402
Ticket #47377 - make listen backlog size configurable

https://fedorahosted.org/389/ticket/47377
Reviewed by: nkinder (Thanks!)
Branch: master
Fix Description: Add the attribute nsslapd-listen-backlog-size - this controls
the listening socket connection backlog maximum size.  This corresponds to
the backlog parameter of the listen() system call.  The default value is 128.
Platforms tested: RHEL6 x86_64
Flag Day: no
Doc impact: yes - need to doc the new attribute
Ticket #47375 - flush_ber error sending back start_tls response will deadlock

https://fedorahosted.org/389/ticket/47375
Reviewed by: nkinder (Thanks!)
Branch: master
Fix Description: The deadlock is caused by the client (or intermediary network
device) closing the connection while the server is attempting to write to the
client, to send back the start tls "success" response.  The server will lock
the c_mutex to disconnect the connection in this error case.  Since the c_mutex
has already been locked in start_tls(), the server will deadlock.  The polling
thread will also attempt to lock c_mutex, deadlocking it too, and the server
will become completely unresponsive.  The fix for this part is to make sure
never to call send_ldap_result with c_mutex locked.
After the server sends back the "success" response, if the
client immediately issues a TLS session negotiation, the server may not
have yet completely set up the socket for TLS, and will attempt to use the
partially setup socket, which can crash.  The fix for this is to setup the
socket for TLS IO using a Conn_IO_Layer callback, to establish the TLS IO
for the connection before the next read() operation.
Platforms tested: RHEL6 x86_64
Flag Day: no
Doc impact: no
(cherry picked from commit ae38b5fc5a40247e52bab960146ed23b286e05f6)