fn: reduce lbagent and agent dependency (#938)

* fn: reduce lbagent and agent dependency

lbagent and agent code is too dependent. This causes
any changed in agent to break lbagent. In reality, for
LB there should be no delegated agent. Splitting these
two will cause some code duplication, but it reduces
dependency and complexity (eg. agent without docker)

* fn: post rebase fixup

* fn: runner/runnercall should use lbDeadline

* fn: fixup ln agent test

* fn: remove agent create option for common.WaitGroup

api/runnerpool/runner_pool.go

@@ -41,7 +41,7 @@ type Runner interface {
 // RunnerCall provides access to the necessary details of request in order for it to be
 // processed by a RunnerPool
 type RunnerCall interface {
-	SlotDeadline() time.Time
+	LbDeadline() time.Time
 	RequestBody() io.ReadCloser
 	ResponseWriter() http.ResponseWriter
 	StdErr() io.ReadWriteCloser