Fix style in connector module

This PR cleanes the style in the connector module (the branchname may not be
appropriate here..., please don't mind!).

This PR also introduces a logic-fix, so it is not _entirely_ about style.

@neithernut Please review carefully (the logic-fix), I am (/ we are)
not entirely sure about it,...
The initial intent was to try flushing stuff as long as writing to the fd doesn't block. However, this was overlooked when working on the `ws_connector_flush()` method.
As it _should_ return `-EAGAIN` if no more data can be written atm, this _should_ be a legetimate fix.