Improvement on Code Redundancy in EC2 VPC

[james03160927]

We created the following resources that relates to EC2 VPC:

• internet Gateways
• EgressOnly internet Gateways
• Endpoints
• NetworkInterfaces
• Subnets
• Nacls
• SecurityGroups
• DHCP options

RIght now, there seems to be quite a lot of code redundancy. Pretty much similar code exist in ec2_vpc.go and all the new resources. We need to update the code something like this: #680

Also, we need to control checking default vs. non-default identifiers for the following functions:

• nukeNacls
• nukeDhcpOptions