disable connector flow-control with channels since they do their own flow control

We have a proxy that uses the connector to connect two SSH channels together. This generally works well, however there are times where the network activity seems to stall. I found that disabling the flow control flags for channels avoided the stall, which seemed to make sense since the channels should be doing their own flow control. I am not sure if this is the best solution, but it works for us, and is submitted for your consideration. I was never able to get the test suite set up, so this has only been tested for what I needed it for.

Checklist

• Commits have Signed-off-by: with name/author being identical to the commit author
• Code modified for feature
• Test suite updated with functionality tests
• Test suite updated with negative tests
• Documentation updated

Reviewer's checklist:

• Any issues marked for closing are addressed
• There is a test suite reasonably covering new functionality or modifications
• Function naming, parameters, return values, types, etc., are consistent and according to CONTRIBUTING.md
• This feature/change has adequate documentation added
• No obvious mistakes in the code