tests: fixed "check meters update"

grep -q exit immediately with zero status if any match is found.
Hence, when executing "ovs-ofctl dump-flows br-int | grep -q meter_id=1",
ovs-ofctl might fail (with error "write to stdout failed") due to the broken pipe.

Signed-off-by: Xavier Simonart <xsimonar@redhat.com>
Acked-by: Ales Musil <amusil@redhat.com>
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
(cherry picked from commit 3869f2e)

tests/ovn.at

@@ -30510,7 +30510,7 @@ ovn-nbctl --wait=hv ls-copp-add copp0 sw0
 check ovn-nbctl --wait=hv sync
 
 AT_CHECK([as hv1 ovs-ofctl -OOpenFlow15 dump-meters br-int | grep -q rate=10], [0])
-AT_CHECK([as hv1 ovs-ofctl dump-flows br-int | grep -q meter_id=1], [0])
+AT_CHECK([as hv1 ovs-ofctl dump-flows br-int 2>&1 | grep -q meter_id=1], [0])
 
 # Update existing meter
 check ovn-nbctl --may-exist meter-add meter0 drop 20 pktps
@@ -30524,7 +30524,7 @@ check ovn-nbctl --log --severity=alert --meter=meter1 \
                 --name=dns acl-add sw0 to-lport 1000 'udp.dst == 53' drop
 check ovn-nbctl --wait=hv sync
 AT_CHECK([as hv1 ovs-ofctl -OOpenFlow15 dump-meters br-int | grep -q rate=30], [0])
-AT_CHECK([as hv1 ovs-ofctl dump-flows br-int | grep -q meter_id=2], [0])
+AT_CHECK([as hv1 ovs-ofctl dump-flows br-int 2>&1 | grep -q meter_id=2], [0])
 
 # Remove meter0
 check ovn-nbctl meter-del meter0
@@ -30542,7 +30542,7 @@ check ovn-nbctl --log --severity=alert --meter=meter2 \
 check ovn-nbctl meter-add meter2 drop 100 pktps
 check ovn-nbctl --wait=hv sync
 AT_CHECK([as hv1 ovs-ofctl -OOpenFlow15 dump-meters br-int | grep -q rate=100], [0])
-AT_CHECK([as hv1 ovs-ofctl dump-flows br-int | grep -q meter_id=1], [0])
+AT_CHECK([as hv1 ovs-ofctl dump-flows br-int 2>&1 | grep -q meter_id=1], [0])
 
 check ovn-nbctl meter-del meter2
 AT_CHECK([as hv1 ovs-ofctl -OOpenFlow15 dump-meters br-int | grep -q rate=100], [1])