Disable preinstalled carrier apps earlier in boot.

Preinstalled carrier apps start in state DEFAULT (== ENABLED); the
telephony stack marks them as DISABLED_UNTIL_USED during
initialization, and eventually ENABLED once a SIM for that carrier is
inserted.

However, this can cause a race as telephony initialization may happen
after the carrier app is started, while it is still in the DEFAULT
state. In this case, the app is disabled, and though PackageManager
will subsequently kill it, this may lead to a race as the app will
briefly remain running while disabled. In this state, crashes are
likely to occur in the app.

So, make sure we perform the first disable as soon as PackageManager
is ready. This ensures the app is not started until it has been
explicitly enabled.

Bug: 27821069
Change-Id: I771d7dde7880fd98b1df3d011be44164abf402f4