Update testFirewallBlocking to check uid chain

If the uid chain is enabled at test start time, testFirewallBlocking
clears the uid chain at the beggining and enables it at the end of the
test to restore the state.

Test: m ConnectivityManagerTest#testFirewallBlocking
Bug: 262141231
Change-Id: I2a9f34794b93cb4f8d111bcade45c23ba6d9bfff
1 file changed