Fixed the race condition for data unthrottling

The retry happened before data throttler has a chance
to unthrottle the APN. Fixed by listening the throttle
status changed event from the throttler, and then retry.

Fix: 196756946
Test: Manual
Merged-In: Ia107f0c49fa293709eb30a27cf70a58e4f929ce0
Change-Id: Ia107f0c49fa293709eb30a27cf70a58e4f929ce0