Galaxy v2 - upstream response href fields are not rewritten

[briantist]

Hitting an endpoint like /api/v2/collections/community/general/versions/ or /api/v2/collections/community/general/versions/4.8.6/ or something, shows the upstream URL in the href field, not the galactory URL.

Luckily this field is not used in ansible-galaxy operations but it should probably be fixed. I probably introduced this in #104 either as a side-effect or while fixing #103.

v3 is not affected simply by way of it not returning absolute URLs, so the relative URL fragments it returns are accidentally correct.