selftests: openvswitch: Add version check for pyroute2

Paolo Abeni reports that on some systems the pyroute2 version isn't
new enough to run the test suite.  Ensure that we support a minimum
version of 0.6 for all cases (which does include the existing ones).
The 0.6.1 version was released in May of 2021, so should be
propagated to most installations at this point.

The alternative that Paolo proposed was to only skip when the
add-flow is being run.  This would be okay for most cases, except
if a future test case is added that needs to do flow dump without
an associated add (just guessing).  In that case, it could also be
broken and we would need additional skip logic anyway.  Just draw
a line in the sand now.

Fixes: 25f16c87

 ("selftests: add openvswitch selftest suite")
Reported-by: Paolo Abeni <pabeni@redhat.com>
Closes: https://lore.kernel.org/lkml/8470c431e0930d2ea204a9363a60937289b7fdbe.camel@redhat.com/


Signed-off-by: Aaron Conole <aconole@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>