Add CHANGE_NETWORK_STATE and INTERNET permission for IpClientRootTests.

Some root test cases create a NetworkAgent to request a network and
send UDP packets on that network, e.g. Send UDP packets after IPv4
provisioning to trigger the tap interface to do the address resolution
process. Add the required permissions for root tests, then we can delete
@SignatureRequiredTest annotation on test cases.

Test: atest NetworkStackRootTests
Change-Id: If5902ba52db6381c2c178e9193c655042ec842a2