[aws|elb] fixes for mock tests

lib/fog/aws/requests/elb/create_load_balancer.rb

@@ -75,7 +75,7 @@ module Fog
           dns_name = Fog::AWS::ELB::Mock.dns_name(lb_name, @region)
           self.data[:load_balancers][lb_name] = {
             'AvailabilityZones' => availability_zones,
-            'Subnets' => options[:subnet_ids],
+            'Subnets' => options[:subnet_ids] || [],
             'Scheme' => options[:scheme].nil? ? 'internet-facing' : options[:scheme],
             'SecurityGroups' => options[:security_groups].nil? ? [] : options[:security_groups],
             'CanonicalHostedZoneName' => '',

lib/fog/aws/requests/elb/describe_load_balancers.rb

@@ -108,7 +108,7 @@ module Fog
           }
 
           if next_marker
-            response.body['DescribeLoadBalancersResult']['NextMarker'] = next_marker
+            response.body['DescribeLoadBalancersResult']['NextMarker'] = next_marker.to_s
           end
 
           response

tests/aws/requests/elb/helper.rb

@@ -37,7 +37,7 @@ class AWS
       })
 
       DESCRIBE_LOAD_BALANCERS = BASIC.merge({
-        'DescribeLoadBalancersResult' => {'LoadBalancerDescriptions' => [LOAD_BALANCER]}
+        'DescribeLoadBalancersResult' => {'LoadBalancerDescriptions' => [LOAD_BALANCER], 'NextMarker' => Fog::Nullable::String}
       })
 
       POLICY_ATTRIBUTE_DESCRIPTION = {