Remote door tweaks

[pevogam]

Adjust remote door file transfer port in case of custom choices and shorten remote door's control file output to a readable length both of which are small tweaks to make the remote door slightly more flexible.

These changes also allow us to run avocado tests with a remote spawner and perform distributed testing.

[pevogam]

Thanks! Note that we still log the complete error via an error level logging message, we just abbreviate it for the final thrown error which often ends up in a test status or other circumstance where one would expect a short error message.