b=4030

b=4030
r=adilger

- new obd method ->o_connect_post() is called when reverse import
  gets initialized
- method ->o_llog_connect() gets obd_export, not obd_device
- MDS passes mdsnum in connect_flags slot
- OST saves last known group in LAST_GROUP file
- OST initializes all known groups upon startup, not on demand
- filter_connect_post() initializes context for given group upon
  connection from MDS
- filter_connect() initializes group from connect_flags
- osc_set_info() doesn't forward "mds_conn": no need to do this any more