tests: Fix flaky test "IPv6 Neighbor Solicitation for unknown MAC"

Fixes: 9ac5485 ("pinctrl: Send RARPs for external ipv6 interfaces")

Acked-by: Ales Musil <amusil@redhat.com>
Signed-off-by: Xavier Simonart <xsimonar@redhat.com>
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
Signed-off-by: Ales Musil <amusil@redhat.com>
(cherry picked from commit f6edbc0)

tests/ovn.at

@@ -13857,8 +13857,9 @@ AT_CHECK([cat 2.packets | cut -c 117-], [0], [expout])
 
 # Check that NS packets are not flooded across routing domains. That means
 # that hv2 should not send any packets across the physical network.
+# Use the grep here to filter out rarp packets that might have arrived
 $PYTHON "$ovs_srcdir/utilities/ovs-pcap.in" hv2/br-phys_n1-tx.pcap | \
-trim_zeros > 2.packets
+grep -v ffffffffffff | trim_zeros > 2.packets
 AT_CHECK([cat 2.packets], [0], [])
 
 # Now send a packet with destination ip other than
@@ -13898,8 +13899,9 @@ AT_CHECK([cat 2.packets | cut -c 117-], [0], [expout])
 
 # Check that NS packets are not flooded across routing domains. That means
 # that hv2 should not send any packets across the physical network.
+# Use the grep here to filter out rarp packets that might have arrived
 $PYTHON "$ovs_srcdir/utilities/ovs-pcap.in" hv2/br-phys_n1-tx.pcap | \
-trim_zeros > 2.packets
+grep -v ffffffffffff | trim_zeros > 2.packets
 AT_CHECK([cat 2.packets], [0], [])
 
 OVN_CLEANUP([hv1])