I0afdda023208c3f8620cb5b89add66448af596d7 added some assertions
to ensure NetworkAgentInfo can only be accessed from the handler
thread. This is good to eliminate any potential concurrent
accessing problem. Howver, dumpsys runs on binder thread, this
change breaks dumpsys functionality.
Thus, this change:
1. Copy Handler#runWithScissors() and related class
locally since they are @hide methods.
2. Run doDump on the handler thread and waits for return.
Test: adb shell dumpsys connectivity
Test: atest FrameworksNetTests:android.net.connectivity.com.android.server.HandlerUtilsTest
Fix: 303348620
Change-Id: Ic3a22f5d370bbf8c18b1972e86d695b6ad61bd0d
f8dba342f1