chore: cleanup tests

[cthomas-newrelic]

Since we've been sing the new vpn, some tests fail due to odd networking exceptions in Mockito.

• DRY's up connection mocking code

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 91.66667% with 1 line in your changes missing coverage. Please review.

Project coverage is 57.50%. Comparing base (a2247fc) to head (f644a97). Report is 2 commits behind head on develop.

Files with missing lines	Patch %	Lines
.../newrelic/agent/android/payload/PayloadSender.java	90.90%	0 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #305 +/- ## ============================================= + Coverage 57.48% 57.50% +0.01% - Complexity 3393 3396 +3 ============================================= Files 328 328 Lines 16800 16803 +3 Branches 1833 1835 +2 ============================================= + Hits 9658 9662 +4 Misses 6105 6105 + Partials 1037 1036 -1 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.