[Issues] MasterFlat missing the overscan correction option

[Philippe Heraudeau]

Hi All,

The MasterFlat recipe misses the overscan correction option,  which 
means it will pick up the last created master dome and master twilight
indpendant of their overscan correction  parameter.
This should be updated to  be consistent  with the dome and twilight 
creation and avoid using the wrong master dome or twilight.

Cheers,
Philippe