In ZmqDriver's listen method, it calls create_consumer
three times. After the first call, the keys related to this
topic in redis reads like this:
"topic": set(["topic.host"])
"topic.host": ""
If the second call, it tries to add the following keys:
"topic.host": set(["topic.host.host"])
"topic.host.host": ""
But the key "topic.host" already exists as a string type.
So the error occurs.
To resolve this problem, change the value of keys from string
to set.
Change-Id: Ic801393d492d2656fcfd8b87f1d2efc6ab3bbd62
Closes-Bug: #1290772
8eed6bbd09