Add and use install_package shell function

This is much more convenient that having different ways to check if a
package is installed or not and then install it, in many different
places.

Also have a install_git function, since the name of the git package
might change, depending on the distro.
Use BASH_COMMON instead of BASH_COMMON_PKG in nova:smoke_tests

The configure_noauth function is used there.
Preliminary (and incomplete) openSUSE support

This enables building packages, which is a good first step.