osd: be a bit more verbose on startup

load_pgs can take a while and it is nice to know what ceph-osd is doing 
without cranking up logging.

Did a quick audit of dout(1)'s and making this the default.  This lets us see
basic OSD state changes (load_pgs, boot, active) at the default level.

At this point all osd state changes should be logged at level 1.

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