Chunk server: use 64 bit integers in the remote sync state machine session expiration logic. Do not attempt to update remote sync state machine session key unless the current key expires in 30 minutes or less in order to minimize the cost of connection establishment and authentication.
Client library: fix session expiration re-connect condition.
Merge branch 'topic/krb' into topic/cs_threads

Conflicts:
	src/cc/chunk/RemoteSyncSM.cc
	src/cc/chunk/RemoteSyncSM.h