Add a basic concurrency test for the dataplane system tests (#832)

Add a basic concurrency test for the dataplane system tests. Also remove some spurious logging.

api/agent/lb_agent.go

@@ -30,8 +30,6 @@ func RequestReader(c *Call) (io.ReadCloser, error) {
 		return nil, errors.New("Call doesn't contain a request")
 	}
 
-	logrus.Info(cc.req)
-
 	return cc.req.Body, nil
 }
 

api/agent/nodepool/grpc/grpc_pool.go

@@ -311,7 +311,7 @@ func (r *gRPCRunner) TryExec(ctx context.Context, call agent.Call) (bool, error)
 	switch body := msg.Body.(type) {
 	case *pb.RunnerMsg_Acknowledged:
 		if !body.Acknowledged.Committed {
-			logrus.Errorf("Runner didn't commit invocation request: %v", body.Acknowledged.Details)
+			logrus.Debugf("Runner didn't commit invocation request: %v", body.Acknowledged.Details)
 			return false, nil
 			// Try the next runner
 		}

api/agent/pure_runner.go

@@ -544,8 +544,6 @@ func creds(cert string, key string, ca string) (credentials.TransportCredentials
 	}), nil
 }
 
-const megabyte uint64 = 1024 * 1024
-
 func createPureRunner(addr string, a Agent, creds credentials.TransportCredentials) (*pureRunner, error) {
 	var srv *grpc.Server
 	if creds != nil {
@@ -565,8 +563,10 @@ func createPureRunner(addr string, a Agent, creds credentials.TransportCredentia
 	return pr, nil
 }
 
+const megabyte uint64 = 1024 * 1024
+
 func getAvailableMemoryUnits() uint64 {
 	// To reuse code - but it's a bit of a hack. TODO: refactor the OS-specific get memory funcs out of that.
 	throwawayRT := NewResourceTracker().(*resourceTracker)
-	return throwawayRT.ramAsyncTotal
+	return throwawayRT.ramAsyncTotal / megabyte
 }