Revert "Don't select backend only shipping rates by default"

This reverts commit 2a3f91229f65e1c0c7e16eb47da455d3488195bc.
Don't select backend only shipping rates by default

As frontend users shouldn't select shipping rates only meant to be used
via backend. So Estimator by default only marks frontend/generic
shipping rates as selected

Fixes #3287
Merge branch 'watg' of github.com:watg/spree into watg
change price_in in variant.rb