Restore puppet module for provisioning memcached

The default caching configuration for MediaWiki-Vagrant is redis, but
having memcached available can be helpful for debugging some issues.
A follow up commit will provide a role to configure the wikis to use
memcached.

This reverts commit e7e232988bdfa641a3c21ff9418326f77f739177.

Change-Id: I5f214dd9b80632fdd44384f44f5fd40e40d8684e
Merge "Restore puppet module for provisioning memcached"