[libvirt] [ruby-libvirt] Allow to set URI via environment variable

[Chris Lalancette]

On Tue, Jan 7, 2014 at 4:11 PM, Guido Günther <agx at sigxcpu.org> wrote:
> This allows us to run tests with the destdriver like:
>
>   RUBY_LIBVIRT_TEST_URI=test:///default \
>   RUBYLIB=lib/:ext/libvirt/ \
>   ruby tests/test_open.rb
> ---
> I've only converted three modules so far since they were simple but
> these already help to run tests during package build.

Looks like a good change.  Applied.  Thanks!

Chris