common_init: remove dup lockdep message

Signed-off-by: Sage Weil <sage@inktank.com>
Revert "RWLock: don't assign the lockdep id more than once"

This reverts commit 957ac3cbe394473f225ffd2b632461fcdaca99e6.

It's important to assign these for all operations for cases where
g_lockdep isn't yet true when the constructor runs.  This is true
for the HeartbeatMap rwlock, among other things, as that thread
is created during early startup before lockdep is enabled.  All
of the lockdep hooks assume that they can assign ids on the fly
and not tracking them here breaks things.

Conflicts:

	src/common/RWLock.h
RWLock: make lockdep id mutable

This allows us to keep the lock/unlock methods const, as per commit
970d53fc0fefc89ffe7550880a4aaa36bd534955.

Signed-off-by: Sage Weil <sage@inktank.com>