OSD support for blkin (LTTng + Zipkin) tracing

Adds tracing for OSDs and Placement Groups, specifically:
messages for OSD operations, FileJournal, FileStore,
ECBackend, replication, and reading and writing traces.
Moves global_init_daemonize() earlier in ceph_osd.c:main

These changes are Marios', with the following exceptions:
 - split out OSD support from other tracing changes
 - only Message.h includes blkin, as others include Message.h
 - commented code has been removed
 - whitespace issues have been fixed
 - braces added to conditionals to match recommended coding style
   - note: did not change member variable names to use m_ prefix
           since member vars in same class did not
 - Ref suffix added to TrackedOp shared_ptr vars to be consistent
   - note: did not add -Ref suffix to ZTrace*Ref vars

Signed-off-by: Andrew Shewmaker <agshew@gmail.com>