Further work on issue #7307399: Framework needs a new pre-user-shutdown...

...phase & callback API

I realized there were a few things wrong with what was there.  The new
ACTION_USER_STARTING was not being sent for the first user at boot, and
there was an existing problem where ACTION_USER_STARTED was sent every
time there was a user switch.

Also improved some debug output of broadcasts to make it easier to see
what is going on in this stuff, and better reporting of why a service
couldn't be started.

Change-Id: Id8a536defbbad1f73d94a37d13762436b822fbe3