Netcat is not a direct dependancy of memcached nor the playbooks in
this role, however other OSA roles delegate tasks to the memcached
container and run shell commands which use nc.
This patch ensures that netcat is explicity installed into the
memcached container and we do not rely on it being present in the
container base image.
Given that the memcached_test_distro_packages variable is no longer
used, the associated bits for it are also removed.
Change-Id: Id046aa97ed90654f1859e584891fe5228f96aa90
261db5b883