Drop unneeded parameters from templates calls

Zuul automatically pass the repository basename to invoked templates.
The feature has been added with https://review.openstack.org/#/c/62500/

In the extensions templates, replace 'extname' with 'name' and remove
all extname: parameters.

This change is a noop.

Change-Id: I626ea667932218abb7342da7ac8dbfd691942181