virt-libvirt: Extend test-runner default tests

By default, the runner was running all variants of a single test.
This makes it harder to spot certain types of test-specific problems.
Instead, the runner should run a wider variety of tests, spreading
the variant choices across a range of underlying functionality.

Unfortunately, there's not a cleaner way to specify a wide range of
tests w/o simply listing them all.  However, the list can be read
in from a file, which will help keep the maintenance effort low. I
hard-coded list file path as relative to wherever the test runner
module is located, since there's no reason to over complicate it.

I expect this list will change over time, so this is only a reasonable
starting place. Included are about 80 libvirt tests from across the
board, with at least one positive and one negative test for each topic.
I attempted to pick different operational varients from each set so,
for example, it doesn't just exercize the same set of parameters
repeatidly.

Including the install and remove, they all complete on my intel i7 based
laptop in under 30min, which was found to be reasonable.

Signed-off-by: Chris Evich <cevich@redhat.com>