Emit a warning if RPC calls made with lock.

This patch will log a warning every time a RPC call is made while
a lock is held if the caller has requested it. This should help us
track down performance problems such as the security group refresh
problem recently found in nova.

RPC calls can emit a warning if called with check_for_lock=True
and debugging is turned on.

Sneaks up on bug 1063222.

Change-Id: Ice94093efb3cb95dd58b31d6ba817c7d505c15af
Merge "Emit a warning if RPC calls made with lock."