Issue #37: Add more optional packages needed by lorax

Added at-spi, tigervnc-server-module, and bitmap-fangsongti-fonts to
bootstrap. These packages will no longer spew out an error during a
build because they were missing. There is still and error for
*-redhat-upgrade-dracut, but this is documented in
https://bugzilla.redhat.com/show_bug.cgi?format=multiple&id=1065557.
Since this package is not yet available, but will soon be added, it
should not be removed.

Removed rpm-ostree and kexec-tools-anaconda-addon from the lorax templates.
We don't use these packages and it silences some errors during the build.

Run createrepo each time we bootstrap on the opt repo. It's possible
that we add a new RPM to the OPT_PACKAGES list. If creatrepo doesn't
need to do anything, it takes about 1 second to run. This "slowdown" is
worth it to make sure that the opt repo is always up to date with the
newest RPMs.