selftest/runtime_test/virgl: Disable for all fedora

We can't support vgem on RHEL derived distros so disable this test for
all fedora hosts rather than specific versions.

(From OE-Core rev: c4760d6a52011515b0f931d08f619c7e49e72158)

Signed-off-by: Steve Sakoman <steve@sakoman.com>