Rx: make conn_call_lock and conn_data_lock usage consistent

Rx: make conn_call_lock and conn_data_lock usage consistent

The rx_connection.flags field is protected by the conn_data_lock
but the conn_data_lock is not held everywhere the conn flags
field is altered.  This produces a race that can result in a
deadlock when waiter flags are inadvertently prevented from being
cleared.

The conn_call_lock usage in rx_EndCall which was removed in
Change e169708681eb1bbbb31951b95f68e861a4b01c7e must be restored.
If rx_EndCall never obtains the conn_call_lock it can't ensure
that the thread in rx_NewCall actively checking the calls will
not end up blocking when there is now a call channel that can
be reused.  This usage of conn_call_lock can be removed only
if a true producer/consumer model is implemented.

Change-Id: Id093fd6c4a42afb833c775411be0cd406abf4ef7
Reviewed-on: http://gerrit.openafs.org/1766
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>