worker: allow enqueueing OSBuild job with multiple dependencies

Change the definition of `EnqueueOSBuildAsDependency()` function to
accept a slice of job IDs on which the OSBuild job depends. Previously,
only the manifest job ID was accepted as the only possible dependency.
This change will be needed in order to enqueue OSBuild jobs for Koji,
which depends on two jobs.

internal/cloudapi/v2/server.go

@@ -153,7 +153,7 @@ func (s *Server) enqueueCompose(distribution distro.Distro, bp blueprint.Bluepri
 			Build:   ir.imageType.BuildPipelines(),
 			Payload: ir.imageType.PayloadPipelines(),
 		},
-	}, manifestJobID, channel)
+	}, []uuid.UUID{manifestJobID}, channel)
 	if err != nil {
 		return id, HTTPErrorWithInternal(ErrorEnqueueingJob, err)
 	}