- metadata_smain
- need destructor that should call leave
- code the TODO in leave from lock_client_cache
- when the person holding the extent fails then we have to go to the server and get the membership
- do the diffs
- periodic puts of the extent data
-getextent client just assumes that it can properly get the  data from a peer when that peer might not exist and needs to go to the server and find updated list as well as ask the server for the extent