Fix waitForBroadcastIdle()

Any ongoing deferrals are fast-forwarded for immediate deliverability,
to minimize the wait time.  Also adds detailed queue state description
to the wait-for-broadcast-idle shell command's output:

Waiting for queue background to become idle...
0 parallel; 0 ordered, 9 deferred
Waiting for queue background to become idle...
0 parallel; 1 in flight, 0 ordered, 8 deferred
...
Waiting for queue background to become idle...
0 parallel; 1 in flight, 5 ordered, 2 deferrals in alarm recipients
All broadcast queues are idle!

Fixes: 123999376
Test: atest CtsVoiceSettingsTestCases
Test: atest CtsBackgroundRestrictionsTestCases
Test: atest CtsAppSecurityHostTestCases:StorageHostTest
Change-Id: Ia0ada70b621131f8bad8e8340083347c5574e4af