Wrap the watch rule start in a method

This is the first step in making the watch task dependant on:
1) whether we even have an alarm in the stack
2) whether the alarm is a ceilometer alarm

The test confirms the current behaviour, which is a periodic task
is created whether or not a watch is in the stack.

bug 1202031
Change-Id: Iebb948f788270fca0dbef61a2e122fe3900d84b2
Merge "Wrap the watch rule start in a method"