E0d/fix feature flag

@ormsbee 
@jimabramson

New version against the RC, with the common.py change.

The remove line overwrites, incorrectly, the value set at

https://github.com/edx/edx-platform/blob/178b82c685da78ecd98e875ec683bd4477fd812a/lms/envs/aws.py#L147

The value in config is under MITX_FEATURES, so we're defaulting to False.