Import _build_current_repodata from conda_index instead of conda_build

[atrawog]

Importing _build_current_repodata has been deprecated in conda_build: https://github.com/search?q=repo%3Aconda%2Fconda-build%20_build_current_repodata&type=code

This PR uses the new conda_index module for importing _build_current_repodata instead of the deprecated functionality in conda_build .

[wolfv]

Hmm, weird that the tests are timing out. Did you try running them locally?

[atrawog]

Thinks work fine in my local test environment. But I haven't looked yet into what versions of conda_build and conda_index are getting used by the github test environment at the moment.

[DerThorsten]

closed via #693