Resolve ambiguous argument.

CTS tests don't have access to TestNetworkAgent and therefore
require overloading this method, which means 'null' is ambiguous.

Bug: 139268426
Test: FrameworksNetTests
Change-Id: I5d7deea82d7114fa38f37b90f94fe7e6073bd848
(cherry picked from commit ff83f1d7eea38c4143869cbf10dca5972421f6cd)
1 file changed