tests: Fix IPFIX test cases issue.

tests: Fix IPFIX test cases issue.

IPFIX statistics 'tx pkts' means the number of successfully
sending IPFIX packets, while 'tx errs' means sending error
IPFIX packets. These two parameters can be affected by whether
listening on port 4739 on local host. This case should be
solved entirely by introducing PARSE_LISTENING_PORT as sFlow,
but it depends on implementing IPFIX packet analysis and it
will take some time. Disable these field first, as IPFIX statistics
check are failed on Windows due to 'tx pkts' and 'tx errs' fields.
Windows marks all packets sending successfully, even if port 4739
on local host is not listened.

Remove XFAIL check for 'Flow IPFIX sanity check - tunnel set',
as this test had “UNEXPECTED PASS” on Windows.

More detail, please refer the following link.
https://www.mail-archive.com/dev@openvswitch.org/msg65229.html

Reported-by: Paul Boca <pboca@cloudbasesolutions.com>
Acked-by: Paul Boca <pboca@cloudbasesolutions.com>
Signed-off-by: Benli Ye <daniely@vmware.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>