Add instrumentation to test NetworkAgent.

Test: NetworkAgentTest, new tests using this API
Bug: 139268426
Change-Id: I0b65be788bb742fd1a8c0ca624e97368462f9b6a
Merged-In: Ia83b1c896df63bb18e2aa4b74d6cc09eba990eb5
(cherry picked from commit d89dcb9765b9c73c950661faaf8af9b795934acb, aosp/1284574)
1 file changed