ci: set GOTRACEBACK=all

Currently when there's a timeout or panic, the culprit goroutines might
not be printed. Set traceback to all, which prints all user created
goroutines.

Change-Id: I29f87812d2a60f671b3eb172499e24cf70d990b5

Jenkinsfile.public

@@ -11,6 +11,7 @@ pipeline {
     }
     environment {
         NPM_CONFIG_CACHE = '/npm/cache'
+        GOTRACEBACK = 'all'
     }
     stages {
         stage('Build') {