feat(deploy): set timeout via label (!290)

Solves coop-cloud/organising#437

A timeout can be specified globally for a recipe using this label:
`coop-cloud.${STACK_NAME}.timeout=${TIMEOUT:-120}`. This sets the default timeout to 120s. An app specific timeout can be set using the env `TIMEOUT`.

Co-authored-by: Moritz <moritz.m@local-it.org>
Reviewed-on: coop-cloud/abra#290

pkg/upstream/stack/stack.go

@@ -31,6 +31,9 @@ const (
 	ResolveImageNever    = "never"
 )
 
+// Timeout to wait until docker services converge, default is 50s (random choice)
+var WaitTimeout int = 50
+
 type StackStatus struct {
 	Services []swarm.Service
 	Err      error
@@ -457,7 +460,7 @@ func WaitOnService(ctx context.Context, cl *dockerClient.Client, serviceID, appN
 
 	go io.Copy(ioutil.Discard, pipeReader)
 
-	timeout := 50 * time.Second
+	timeout := time.Duration(WaitTimeout) * time.Second
 
 	select {
 	case err := <-errChan: