b=23289 grained lock for ptlrpc service

b=23289 grained lock for ptlrpc service

- cacheline optimization for struct ptlrpc_service
- split ptlrpc_service::srv_lock to three locks:
  . ptlrpc_service::srv_lock
    serialize operations on rqbd and requests queued on srv_req_in_queue
  . ptlrpc_service::srv_rq_lock
    serialized operations on active requests
  . ptlrpc_service::srv_rs_lock
    serialize operations on RS
- cleanup logic in ptlrpc_main()
- remove unused atomic srv_outstanding_replies

o=liang
i=andreas.dilger
i=mikhail.pershin