Fix attempting to update media directories when the site dir is moved.
Fix attempting to update media directories when the site dir is moved.

We had old code that tried to update MEDIA_ROOT when the directory
moved. However, this code was updating the wrong variable (setting
MEDIA_ROOT to the static directory), and never tried to actually fix
STATIC_ROOT. This was clearly wrong, and has been for some time.

We now properly update the two variables based on their respective paths
and settings.

Testing Done:
I hit this issue after moving my source tree around. This fixed it,
setting the correct paths for both variables to their correct new values.

Reviewed at https://reviews.reviewboard.org/r/8038/

chipx86/reviewboard,sgallagher/reviewboard,brennie/reviewboard,chipx86/reviewboard,reviewboard/reviewboard,brennie/reviewboard,sgallagher/reviewboard,davidt/reviewboard,chipx86/reviewboard,brennie/reviewboard,davidt/reviewboard,chipx86/reviewboard,reviewboard/reviewboard,reviewboard/reviewboard,sgallagher/reviewboard,sgallagher/reviewboard,reviewboard/reviewboard,davidt/reviewboard,brennie/reviewboard,davidt/reviewboard