Fixed a transcoding bug that occurred when remote transcoder was removed

[eliteprox]

What does this pull request do? Explain your changes. (required)
This change fixes a bug that caused an orchestrator to lose all transcoders when one of it's transcoders disconnects unexpectedly.

Specific updates (required)

• Simplified logic in removeFromRemoteTranscoders so that correct transcoder is removed from RemoteTranscoderManager

How did you test each of these updates (required)
We tested up to 4 streams going to an orchestrator with up to 4 remote transcoders. We stopped one of the transcoders in the following scenarios and observed streams move to another transcoder without disconnecting any other transcoders.

• 1 stream on each of the 4 remote transcoders
• 2 streams on each of 2 remote transcoders
• 4 streams on 1 transcoder with 3 additional transcoders having 0 load.

In every case we observed the streams safely move to another available transcoder without causing other transcoders to break.

Does this pull request close any open issues?

#2605
#2706

Checklist:

• Read the contribution guide
• make runs successfully
• All tests in ./test.sh pass
• README and other documentation updated
• Pending changelog updated