Only send usb disconnect intents after boot.

This prevents cases where the device starts up and attempts
to change the config, but intents cannot yet be sent.

A patch to resend this skipped intent is necessary to
finish fixing the bug.

Bug: 34451258
Test: Check that usb state is properly handled on boot
Change-Id: I9d79c67ce8982fd5b43fa40781b66bb9ae820694