Clean up unit testing for ConnectivityDiagnostics.

Connectivity Diagnostics included an unnecessary try-catch for verifying
that the permissions check for invoking ConnectivityDiagnosticsCallbacks
doesn't throw when the uid and package name do not match.

Bug: 149119324
Test: atest FrameworksNetTests
Change-Id: Ie302b1f4f437e819fdd15ec28adb0b56750c2c53