Fix Firefogg config order

mw.UploadWizard.config is set, stupidly, in mw.UploadWizard's constructor,
so everything is all out of order. Also, the check for whether Firefogg is
enabled only happened after UW decided to use Firefogg, which obviously
wouldn't happen if we didn't know it was enabled...ugh. Fixed now.

Bug: T77973
Change-Id: Ia703609616cbbd284cd19430aa538a18992a9b1d
Merge "Fix Firefogg config order"