Simplify Building Trove Guest Images

Enable Trove guest images to be build without going through the whole
redstack install, and redstack kick-start workflow. Also seperated out
the upload-to-glance pieces to enable this.

You can now simply build a mysql image using:
redstack build-image mysql

Partially implements blueprint: tempest-guest-tests
Change-Id: I671e22c19e1e11df677959e8f158f26c7da055c8