Refactor remote transcoding tests in orch_test.go to remove time.sleep

[eliteprox]

Is your feature request related to a problem? Please describe. Remote transcoding tests might be flaky due to a time.sleep required with go-routines to connect remote T for testing. There are currently 5 such tests: https://github.com/livepeer/go-livepeer/blob/f07d69da2ddbfbd163e05ccbb90d1c1d47052a95/core/orch_test.go#L33 https://github.com/livepeer/go-livepeer/blob/f07d69da2ddbfbd163e05ccbb90d1c1d47052a95/core/orch_test.go#L186 https://github.com/livepeer/go-livepeer/blob/f07d69da2ddbfbd163e05ccbb90d1c1d47052a95/core/orch_test.go#L243 https://github.com/livepeer/go-livepeer/blob/f07d69da2ddbfbd163e05ccbb90d1c1d47052a95/core/orch_test.go#L346 https://github.com/livepeer/go-livepeer/blob/f07d69da2ddbfbd163e05ccbb90d1c1d47052a95/core/orch_test.go#L422

Describe the solution you'd like Refactor remote transcoding tests inside of orch_test.go to allow for remote transcoders to be connected without using go-routines or time.sleep. As recommended in #2747. One additional test should be added once resolved. I've published this to my branch here: https://github.com/eliteprox/go-livepeer/tree/develop-trancoderdrop-tests

Describe alternatives you've considered Considered leaving the time.sleep in the tests, decision made to not add the new test at this time.

Additional context None