tests: Fix flaky "OVN FDB (MAC learning)".

FDB updates to sb can be delayed up to MAX_FDB_DELAY_MSEC i.e.
50 msec, so there was no guarantee that FDB was updated when
packet was received at destination.

Signed-off-by: Xavier Simonart <xsimonar@redhat.com>
Signed-off-by: 0-day Robot <robot@bytheb.org>

tests/ovn.at

@@ -31789,12 +31789,13 @@ OVN_CHECK_PACKETS([hv2/vif1-tx.pcap], [expected])
 
 wait_row_count FDB 2
 
+# FDB update can be delayed up to MAX_FDB_DELAY_MSEC msec.
+wait_column "$sw0p3_dpkey" fdb port_key mac='"50:54:00:00:00:13"'
+
 check_column "50:54:00:00:00:13 50:54:00:00:00:14" fdb mac
 check_column "$sw0_dpkey $sw0_dpkey" fdb dp_key
 check_column "$sw0p1_dpkey $sw0p3_dpkey" fdb port_key
 
-check_column "$sw0p3_dpkey" fdb port_key mac="50\:54\:00\:00\:00\:13"
-
 as hv1 reset_pcap_file hv1-vif1 hv1/vif1
 as hv1 reset_pcap_file hv1-vif3 hv1/vif3