Inform Application thread to block for network rules to be updated.

Bug: 226299593
Test: atest tests/cts/hostside/src/com/android/cts/net/HostsideRestrictBackgroundNetworkTests.java
Change-Id: Ie37173d0d3f4034a74b834550920530166cd4201
Merged-In: Ie37173d0d3f4034a74b834550920530166cd4201