Adjust the interrupt storm handling code to better handle a storm. When

Adjust the interrupt storm handling code to better handle a storm.  When
a storm is detected, enter "storming" mode which throttles the interrupt
source such that the handlers are run once every clock tick.  Previously
we allowed a full set of storm_threshold interations through the handler
before going back to sleep.  Also, this currently will intentionally exit
storming mode once a second to see if the storm has passed.

Tested by:	marcus
Discussed with:	bde