Fix issue #16907799: Processes containing bound services...

...are killed over eagerly.

When the current foreground activity is moving to the background,
it was briefly going through the CACHED_ACTIVITY state before the
correct LAST_ACTIVITY state, allowing its bound service processes
to be killed (because they went in to the cached list).  To solve
this, as long as a process has stopping activities, it won't go
lower than LAST_ACTIVITY.

Also fixed a problem where we could put a process in CACHED_EMPTY
instead of CACHED_ACTIVITY_CLIENT.  There were a number of cases
in the binding flow and also the client process state transitions
where we would not correctly updateing the bound client activity
state.

And add some sanity code so that if a process hosting a
service is killed, and a client process of that service is in the
cached state, we kill the client process.  This avoids situations
where we can start thrashing around in the cached list because we
are restarting process for no reason -- since they will just
continue to be cached.

Finally, tune the process LRU list to allow twice as many cached
activity processes (from 8 to 16), so we can make better use of
the RAM we have available these days.

Change-Id: Ib0cdf78c321cbb035259fc9dd6ee27b5ba1f90c5