osdc/Objecter: only ping after watch is registered

If we ping before the watch is registered we will get ETIMEDOUT (the ping
is are a read op that will fail to see the watch registration).

Signed-off-by: Sage Weil <sage@redhat.com>
librados: stop using IoCtxImpl lock for watch/notify functions

This is a carry-over from olden times when Objecter didn't do its own
locking.

Signed-off-by: Sage Weil <sage@redhat.com>
librados: remove IoCtxImpl lock member

It is dead!

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