Update the LDAP connection handler so that an operation is removed from the
"operations in progress" queue for the associated client connection immediately
before the response is sent to the client.  This can help avoid race conditions
in which the client immediately re-uses the same message ID for the next
synchronous request and it could be received while post-response processing
is still in progress for that connection.  Previously, this would have caused
the new request to be rejected even though there was technically nothing wrong
with what the client had done.

OpenDS Issue Number:  614