fix ros::master::getTopics() getting worng results

[liangteng]

The declaration of ros::master::getTopic says that each item in the result is a pair <string topic, string type>, but in the implementation the item is a pair of <string topic, string uri> which is conflict with declaration.

Besides, the TopicInfo is a container of topic name and datatype, not uri

[CLAassistant]

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