Ocassionally this exporter produces output which is not compatible
with the telegraf prometheus input plugin. This change adds a filter
to remove duplicated HELP and TYPE texts from the output
eg:
021-09-13T19:40:00Z E! [inputs.prometheus] Error in plugin: error
reading metrics for http://10.96.22.16:9103/metrics: reading text
format failed: text format parsing error in line 46: second HELP
line for metric name "openstack_services_neutron_neutron_sriov_nic_agent"
Change-Id: I8c4c7739be86207de04bca4c1f9718794f4dda5f