Replica + Arbiter number validation

[tsmgeek]

https://github.com/voxpupuli/puppet-gluster/blob/master/manifests/volume.pp#L186-L197

When support for arbiters was added the validation was removed to check correct amount of bricks was defined.

Regardless of if there is an arbiter defined, the amount of bricks should be a multiple of replica setting so maybe it can be checked.