Modify Marconi2024_Server.py, fix yield stmt
Fix syntax errors in SWEEP_CONTROL.py

The sweep control widget will run when called directly from python,
the labrad manager recognizes a new client (from the connectAsync),
but the QtMainWindow for the widget does not show up.

Similar actions for the TRAPDRIVE_CONTROL and TICKLE_CONTROL allow
the window to show up.

Possible source of problem: reactor already installed error.