A new validation check:

* validate_count_as_odd_for_role
  As the name describes we want to check that we have an odd number
  of nodes used in a role.

Signed-off-by: JuanJose 'JJ' Galvez <jj.galvez@inktank.com>
Must specify the version being used for the activesupport gem.
If the version is not specificed it tries the newest which we
can not support on Roxy due to the ruby version in use.

2.3.17 is what is available on the admin server.

Signed-off-by: JuanJose 'JJ' Galvez <jj.galvez@inktank.com>