Use the shared config region when region is not set by command line f…

…lag.

Previously, not including the `--region` flag would result in an error
being thrown and unicreds just stopping.

Now, the session will use the region as set by the environment variable
or inside one of the AWS config files (~/.aws/credentials and
~/.aws/config), if region isn't set by flag.

aws_config.go

@@ -25,10 +25,6 @@ func SetAwsConfig(region, profile *string, role *string) (err error) {
 		}
 	}
 
-	if aws.StringValue(region) == "" && aws.StringValue(profile) == "" {
-		return nil
-	}
-
 	// This is to work around a limitation of the credentials
 	// chain when providing an AWS profile as a flag
 	if aws.StringValue(region) == "" && aws.StringValue(profile) != "" {