Intermittent errors in voltha-go unit tests

Intermittent failures are seen on unit tests. As an example, see https://jenkins.opencord.org/job/verify_voltha-go_unit-test-tests/1470/console

08:21:08     grpc_nbi_api_handler_test.go:578: 
08:21:08         	Error Trace:	grpc_nbi_api_handler_test.go:578
08:21:08         	            				grpc_nbi_api_handler_test.go:705
08:21:08         	Error:      	Expected nil, but got: &errors.errorString{s:"timeout-waiting-devices"}
08:21:08         	Test:       	TestSuite1

Increasing Jenkins VM from 2c-4g to 4c-8g seemed to reduce the quantity of errors, but even with the better provisioned VM, it took several attempts to get a clean run.

1) Examine ways to reproduce (can it be done locally?)

2) Determine whether there is a correctness problem or a performance problem? Is it that the devices didn't change state fast enough, or did they never change state?

3) It could also be a problem with the unit tests themselves...