tests, vmi_networking: remove xfail from IPv6 test
tests, vmi_networking: remove xfail from IPv6 test

The issue that made this test unstable was resolved:
https://github.com/kubevirt/kubevirt/issues/5113
Also, the previous commit allows users to run the tests
in an environment with no outside connectivity and
skip the tests that pings to the outside.
This can help with avoiding similar issues.
For that the xfail is no longer necessary, and it is
removed by this commit.

Signed-off-by: alonsadan <17e3534da4e06ee40320bd1687715e3dda4806ac@redhat.com>

davidvossel/kubevirt,davidvossel/kubevirt,stu-gott/kubevirt,kubevirt/kubevirt,davidvossel/kubevirt,kubevirt/kubevirt,stu-gott/kubevirt,stu-gott/kubevirt,kubevirt/kubevirt,stu-gott/kubevirt,davidvossel/kubevirt,kubevirt/kubevirt