Send LOCKED_BOOT_COMPLETED on same queue as BOOT_COMPLETED

Make sure that the LOCKED_BOOT_COMPLETED broadcast is dispatched via the
same delivery queue as BOOT_COMPLETED.  Currently, it's possible for an
app to receive the two broadcasts in reverse order, which violates the
start sequence contract.

Bug: 149030767
Test: boot & observe LOCKED_BOOT_COMPLETED / BOOT_COMPLETED history
Change-Id: Ib44d53a0c97a24ec648e1d9c9057464f6cb331d8