tests: Ignore "Connection refused" in learning-switch test.

After terminating ovs-testcontroller, vswitchd may attempt to
reconnect before test cleanup completes resulting in a "Connection
refused" log message and the test to fail. This can be reliably
reproduced by inserting a 1-second sleep before log checking.

This patch filters out "Connection refused" messages for check_log to
prevent erroneous test failures.

Reported-at: https://redhat.atlassian.net/browse/FDP-1813
Fixes: 70ba6e9 ("learning-switch: Fix coredump of OpenFlow15 learning-switch.")
Acked-by: Eelco Chaudron <echaudron@ovn.org>
Signed-off-by: Mike Pattrick <mkp@redhat.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

Author: mkp-rh

tests/learning-switch.at

@@ -19,5 +19,6 @@ AT_CHECK([
 AT_CHECK([kill `cat ovs-testcontroller.pid`])
 
 OVS_WAIT_UNTIL([! test -e controller])
-OVS_VSWITCHD_STOP(["/cannot find route for controller/d"])
+OVS_VSWITCHD_STOP(["/cannot find route for controller/d
+/Connection refused/d"])
 AT_CLEANUP