librados: avoid unnecessary locks

librados: avoid unnecessary locks

Revise wait_for_osdmap to be called outside of RadosClient::lock
and only take the lock if it has to wait for a map.

Also, now that objecter handles its own locking nicely,
there are various places where it is no longer necessary
for RadosClient to take its own lock -- all the calls that
go directly into objecter (RadosClient::pool_*) don't need
to hold RadosClient::lock.

Signed-off-by: John Spray <john.spray@redhat.com>