use Peer::IsClose inline replace RpcClientChannel
Merge branch 'bugfix_rpc-0.1.6.rc' into bugfix_rpc-0.1.6.rc_remove_cancel
 add cancelable into RpcServer
 add log
 add cancel
 add unittest for CancelableWaitQueue
 add error text
 free memory of session cancelled
 change log
 fixbug: use wrong request num to cancel request
 remove uncessary code
 adjust unittest