Fixed bug with activity moved to pinned stack left in resumed state.

When we move an activities task to the pinned stack, we were checking
if the previous activity stack is the currently focused stack to see
if the activity was resumed. It is possible we changed the focused
stack which will cause this check to fail and we will fail to detect
that the activity was in the resumed state there by failing to transition
it to the paused state. We now only check that the activity is the
resumed activity in the previous stack which is sufficient.

Bug: 28023315
Change-Id: I0782f385b7ee53307ed9c95e3048bcb4353463f7