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/server/runner.go

@@ -75,7 +75,7 @@ func (s *Server) serve(c *gin.Context, app *models.App, path string) error {
 
 	call, err := s.agent.GetCall(
 		agent.WithWriter(&writer), // XXX (reed): order matters [for now]
-		agent.FromRequest(app, path, c.Request),
+		agent.FromRequest(s.agent, app, path, c.Request),
 	)
 	if err != nil {
 		return err