Bugfix: Ignore "checksum" parameter in copy module

When copying, recent versions of ansible set the "checksum" field of the
json-payload for validation of the file after copy. As of now, we simply
ignore the parameter.

src/copy.lua

@@ -32,6 +32,8 @@ function main(arg)
 		, validate = { required=false, type='str' }
 		, directory_mode = { required=false }
 		, remote_src = { required=false, type='bool' }
+		-- sha256sum, to check if the copy was successful - currently ignored
+		, checksum = {}
 
 
 		-- file common args