PollingMonitor now can have the timeout range modified while running.

To allow derived/custom server more control over how often they poll,
we needed to change a PollingMonitor while it active.

Change-Id: Ia5a66847b8e82713a405361fbd93f3513d8da232
Allow a user to change the range at which a server can poll at.

When trying to create highly responsive servers that need to shutdown fast,
we need the ability to set a really low poll interval range so that the
poll operation doesn't block the destruction for a long time.

This will also allow users to create servers that run in immediate mode,
if they just have to burn cpu cycles.

Change-Id: Ib7a76b66c0ab1f4cd742c17e1022de42d86ab5dc