SCVMM scheduled EMS refresh.

A mechanism was needed to refresh the SCVMM provider given that event support will not be in the 3.1 release. I have configured a 4 minute schedule but am open to negotiation on the frequency. On one hand we need to bear in mind that an EMS refresh can take more than 4 minutes but on the other hand we can't wait too long after a VM power operation.
Do you think we should bump this up to `15.minutes` by default.  If users want a more aggressive schedule, they can change it.  And, we can even ask if QE will test a more aggressive schedule.

I'm a little worried that 4 minutes isn't enough time to handle decent sized deployments.  And, if the worker gets behind the schedule, it could back up the queue.

If we give it enough time out of the box, then at least any more aggressive schedule is done willingly.

What do you think?