calico: set 1340 as mtu

Author: chrischdi

test/e2e/data/cni/calico/calico.yaml

@@ -45,7 +45,9 @@ data:
   # Configure the MTU to use for workload interfaces and tunnels.
   # By default, MTU is auto-detected, and explicitly setting this field should not be required.
   # You can override auto-detection by providing a non-zero value.
-  veth_mtu: "0"
+  # veth_mtu: "0"
+  # Overwritten the default to prevent connectivity issues in GCVE networking.
+  veth_mtu: "1340"
 
   # The CNI network configuration to install on each node. The special
   # values in this config will be automatically populated.