Revert "Enable Gearman as default on Jenkins slaves"

SERVER: Invalid relationship: File[/var/lib/jenkins/hudson.plugins.gearman.GearmanPluginConfig.xml] { require => Class[Zuul] }, because Class[Zuul]doesn't seem to be in the catalog

This reverts commit 2a9cd677e4eb6a60787ebc73bd8fd9e1b6f26b34
Merge "Revert "Enable Gearman as default on Jenkins slaves""