Reapply "Make iterating over mNetworkAgentInfos safer."

Now that the faulty test is fixed,
This reverts commit 09bc78fda764d57e257df3c59857ca2414d0f6f8.

Test: ConnectivityCoverageTests CtsNetTestCases FrameworksTelephonyTests
Change-Id: If52cc211b7859c0add07c16f171a6ce342ccca97
1 file changed