veyron/services/mgmt/node/impl: updating 'wait for child' timeout to 20s to see
if it helps with mac jenkins test failures.

Change-Id: I490680a78cc3c18b27dda9d86fe5165e44b3babe
diff --git a/services/mgmt/node/impl/app_invoker.go b/services/mgmt/node/impl/app_invoker.go
index 682a5ab..d5bb6eb 100644
--- a/services/mgmt/node/impl/app_invoker.go
+++ b/services/mgmt/node/impl/app_invoker.go
@@ -488,7 +488,7 @@
 		return errOperationFailed
 	}
 	// Wait for the child process to start.
-	timeout := 10 * time.Second
+	timeout := 20 * time.Second
 	if err := handle.WaitForReady(timeout); err != nil {
 		vlog.Errorf("WaitForReady(%v) failed: %v", timeout, err)
 		return errOperationFailed