[aws|compute] Fix a bug in delete_tags, but come up against a bug in AWS where tags aren't deleted if the resource still exists.

lib/fog/aws/requests/compute/delete_tags.rb

@@ -28,7 +28,7 @@ module Fog
             index += 1 # should start at 1 instead of 0
             params.merge!("Tag.#{index}.Key" => key)
             unless tags[key].nil?
-              params.merge("Tag.#{index}.Value" => tags[key])
+              params.merge!("Tag.#{index}.Value" => tags[key])
             end
           end
 

tests/aws/requests/compute/tag_tests.rb

@@ -61,6 +61,8 @@ Shindo.tests('Fog::Compute[:aws] | tag requests', ['aws']) do
       end
     end
 
+    @volume.destroy
+
     tests("#delete_tags('#{@volume.identity}', 'foo' => 'bar')").formats(AWS::Compute::Formats::BASIC) do
       Fog::Compute[:aws].delete_tags(@volume.identity, 'foo' => 'bar').body
     end
@@ -72,6 +74,4 @@ Shindo.tests('Fog::Compute[:aws] | tag requests', ['aws']) do
     end
 
   end
-
-  @volume.destroy
 end