Revert removal of dynamic Mist trigger setup

This broke catalyst E2E Tests. I plan to fix it later, but for now let's revert this removal

handlers/misttriggers/trigger_broker.go

@@ -3,10 +3,10 @@ package misttriggers
 import (
 	"context"
 	"fmt"
-	"github.com/livepeer/catalyst-api/clients"
 	"sync"
 
 	"github.com/golang/glog"
+	"github.com/livepeer/catalyst-api/clients"
 	"golang.org/x/sync/errgroup"
 )
 

main.go

@@ -319,7 +319,7 @@ func main() {
 	if cli.IsClusterMode() {
 		// Configure Mist Triggers
 		if cli.MistEnabled && cli.MistTriggerSetup {
-			mistTriggerHandlerEndpoint := fmt.Sprintf("%s/api/mist/trigger", catalystApiURL)
+			mistTriggerHandlerEndpoint := fmt.Sprintf("%s/api/mist/trigger", cli.OwnInternalURL())
 			err := broker.SetupMistTriggers(mist, mistTriggerHandlerEndpoint)
 			if err != nil {
 				glog.Error("catalyst-api was unable to communicate with MistServer to set up its triggers.")