Move more responsibility to common EC2 module

Moved `AWS_REGIONS` into `ec2` module
Created `ec2_connect` method in `ec2` module
Updated modules able to use `ec2_connect` and `AWS_REGIONS`

library/cloud/ec2_vpc

@@ -164,15 +164,6 @@ except ImportError:
     print "failed=True msg='boto required for this module'"
     sys.exit(1)
 
-AWS_REGIONS = ['ap-northeast-1',
-               'ap-southeast-1',
-               'ap-southeast-2',
-               'eu-west-1',
-               'sa-east-1',
-               'us-east-1',
-               'us-west-1',
-               'us-west-2']
-
 def get_vpc_info(vpc):
     """
     Retrieves vpc information from an instance