init: try to start all OSDs, don't give up on failures

 With multiple OSDs we shall try to start all of them instead of giving up
 when one OSD did not start.

 This fixes the problem when no OSD started if OSD.1 is unable to start
 because its file system is not mounted (which is expected when HDD is
 dead). Since HDDs fail from time to time we should tolerate error(s) and
 try to bring other OSDs up.

Signed-off-by: Dmitry Smirnov <onlyjob@member.fsf.org>