Merge remote-tracking branch 'yan/wip-mds'

Reviewed-by: Sage Weil <sage@inktank.com>
Conflicts:
	src/mds/MDCache.cc

diff --cc src/common/config_opts.h
Simple merge

diff --cc src/mds/Locker.cc
Simple merge

diff --cc src/mds/MDCache.cc
Simple merge

diff --cc src/mds/MDS.cc
Simple merge

diff --cc src/mds/Migrator.cc
Simple merge

diff --cc src/mds/Server.cc
Simple merge

diff --cc src/msg/Message.h
Simple merge