Skip domain verify broadcast if ActivityManager isn't ready

It's possible these are scheduled at boot, before ActivityManager is
ready. If that happens, just skip them.

The domain verification agent is supposed to scan through all the
packages at boot to re-schedule any packages/domains that need
verification, so dropping the install time broadcast at boot isn't a
concern.

Bug: 183127964

Change-Id: Ie44b41a3108253c7cf7702f7f3c08e49223414b4