Enable log based metrics for nova

New prometheus metrics now available:

  * log_messages - total number of log lines per severity
  * openstack_http_response_times - set of HTTP-stats metrics per HTTP method and status:
    - three quantiles, 50%, 90% and 99% for response time
    - sum of response time
    - count of responses

Change-Id: I60b104b3d3579c99616d24c23de02c72c265e5a4
2 files changed