Start the watcher task if a nested stack has watches

Even if the parent stack has no watches.

Change-Id: I06322f908fdbd474778776749cb3e1634183ed23
Partial-Bug: #1234010
Make sure that nested stacks have their watch rules checked

Change-Id: Iee9629739e9549e33f8ed8c4ca08098a7e4d0acf
Closes-Bug: #1234010
Merge "Start the watcher task if a nested stack has watches" into milestone-proposed
Merge "Make sure that nested stacks have their watch rules checked" into milestone-proposed