Refactor tests that use testutil.WaitForResult to use retry.
Since this requires refactoring the test functions in general this patch
also shows the use of the github.com/pascaldekloe/goe/verify library
which provides a good mechanism for comparing nested data structures.
Instead of just converting the tests from testutil.WaitForResult to
retry the tests that performing a nested comparison of data structures
are converted to the verify library at the same time.
* Test fixes in health_endpoint_test.go, agent_endpoint_test.go and rtt_test.go
* Don't reuse the same agent config in TestAgent_ReconnectConfigSettings
Frank Schroeder