Add support for AWS Elastic Fabric Adapter

[james-grant1]

Ansible development to enable EFA support as per support #25

[james-grant1]

Instructions for supporting EFA including installing on different OSes:

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/efa-start.html

[christopheredsall]

EFA is supported by certain instance types. You can get a list by using aws ec2 describe:

$ aws ec2 describe-instance-types --region eu-west-1 --filters Name=network-info.efa-supported,Values=true --query "InstanceTypes[*].[InstanceType]" --output text
i3en.24xlarge
g4dn.metal
m5zn.12xlarge
r5n.24xlarge
m5zn.metal
c5n.18xlarge
c5n.metal
m5dn.24xlarge
inf1.24xlarge
m5n.24xlarge
p3dn.24xlarge
i3en.metal
r5dn.24xlarge