Fix metrics dashboard

[josecelano]

Graphs titles didn't match the filters.

• Some graphs didn't specify it's for UDP4.
• They didn't have a label to filter the IP family (inet), so inet6 was also included. That is not a problem yet becuase we haven't enabled inet6, but it would be when we enabled it.
• It also contains a fix I applied some days ago. For the average processing times, the aggregate function should also be "average" instead of "sum". To calculate the average processing times for all UDP4 connection requests, we have to calculate the average for all the time series:

# HELP udp_tracker_server_performance_avg_processed_requests_total Total number of UDP requests processed for the average performance metrics
# TYPE udp_tracker_server_performance_avg_processed_requests_total counter
udp_tracker_server_performance_avg_processed_requests_total{request_kind="connect",server_binding_address_ip_family="inet",server_binding_address_ip_type="plain",server_binding_ip="0.0.0.0",server_binding_port="6868",server_binding_protocol="udp"} 2710
udp_tracker_server_performance_avg_processed_requests_total{request_kind="scrape",server_binding_address_ip_family="inet",server_binding_address_ip_type="plain",server_binding_ip="0.0.0.0",server_binding_port="6969",server_binding_protocol="udp"} 749970
udp_tracker_server_performance_avg_processed_requests_total{request_kind="connect",server_binding_address_ip_family="inet",server_binding_address_ip_type="plain",server_binding_ip="0.0.0.0",server_binding_port="6969",server_binding_protocol="udp"} 27088948
udp_tracker_server_performance_avg_processed_requests_total{request_kind="announce",server_binding_address_ip_family="inet",server_binding_address_ip_type="plain",server_binding_ip="0.0.0.0",server_binding_port="6969",server_binding_protocol="udp"} 40968541

[josecelano]

ACK 69733c0