Add test for increasing/decreasing the number of active MON pods

[colder-is-better]

• First we make sure the expected (default) number of MON pods are running
• We increase the number of expected MON pods by 2, allowing more than one MON pods per node
• We make sure the new expected number of MON pods are all running
• Finally, we decrease the number of MON pods down to the default number, also disallowing more than one MON pods per node