Set MTU to 9001 when multiple nic are configured in the instance

The change flollows the best practice described in the official guide https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/network_mtu.html

Author: francesco-giordano

cookbooks/aws-parallelcluster-config/files/default/network_interfaces/configure_nw_interface.sh

@@ -33,6 +33,7 @@ BOOTPROTO=none
 IPADDR=${DEVICE_IP_ADDRESS}
 PREFIX=${CIDR_PREFIX_LENGTH}
 GATEWAY=${GW_IP_ADDRESS}
+MTU="9001"
 IPV4_FAILURE_FATAL=yes
 NAME="System ${DEVICE_NAME}"
 EOF

cookbooks/aws-parallelcluster-config/files/ubuntu/network_interfaces/configure_nw_interface.sh

@@ -47,6 +47,7 @@ network:
   ethernets:
     ${DEVICE_NAME}:
 $STATIC_IP_CONFIG
+      mtu: '9001'
       routes:
        - to: 0.0.0.0/0
          via: ${GW_IP_ADDRESS} # Default gateway