Feature: Raise cluster size limit to 16

Background: Historically, VMware used to support only 8 nodes per cluster when using linked clones and hence CloudStack disallowed larger cluster sizes. Over the years, those restrictions no longer exist in in VMware and customers are asking for larger cluster size. One of the most often cited use case is where they put one or more dedicated failover hosts per cluster - in this situation, the smaller cluster size means potentially larger overhead (and hence unused resources). CloudStack actually checks the cluster size when you add a whole VMware cluster into CS and will fail at the point when you add the cluster if cluster size exceeds 8 host.There is a back-door(or bug) that allows to bypass this check, you can do so by adding host separately to the cluster, but this is really not recommended.

Requirements:

• Allow larger cluster size for VMware, both when using linked or non-linked clones