Sensu keepalive handler

This started as just the keepalive handler fix.
But when it wouldn't pass integration tests it expanded:

The undefined 'restart sensu-client' handler cropped up again.  This issue has been showing up in various sense_check module calls. 
Decided to nip this in the bud by researching how Ansible does role dependencies and I found out that you can indicate role deps via meta/main.yml ( within a role dir ).  see http://www.ansibleworks.com/docs/playbooks.html#id12
So any roles that are using the restart sensu-client handler need to have a role dependency against sensu-client setup via meta/main.yml.

In addition, to get things working I had to
- add the common role as a preceeding dependency in the meta/main.yml (otherwise antsy gem was not being found when sensu-client ran )
- add valid sensu server information into the envs/example/group_vars ( otherwise sensu-client would fail to start on CI test instances )