Add extra labels for the Metrics of Redis' Requests

[NeJan2020]

Add extra labels for the Topology Metric and Entity Metric of Redis' Requests.

Entity Metric

Label	Example	Notes
request_content	GET	The command of the Redis request.
response_content	noerror	The value is either error or noerror.

Topology Metric

• status_code: 0 if there is no error; 1 otherwise.

[dxsup]

Please update the changelog.