KNIFE_EC2-51 - EC2 throws ENETUNREACH while instance is firing up
KNIFE_EC2-51 - EC2 throws ENETUNREACH while instance is firing up

This is related to CHEF-1995 which covers the EHOSTUNREACH case. This
just adds the same sleep/retry logic for the ENETUNREACH case.

ivantsepp/knife-ec2,ClogenyTechnologies/knife-ec2,4current/knife-ec2,chef/knife-ec2,chef/knife-ec2,zillabyte/knife-ec2,TheNeatCompany/knife-ec2,cloudant/knife-ec2,tas50/knife-ec2,DataDog/knife-ec2,MsysTechnologiesllc/knife-ec2,evertrue/knife-ec2,pallan/knife-ec2,smith/knife-ec2,MsysTechnologiesllc/knife-ec2,juliandunn/knife-ec2,paperlesspost/knife-ec2