MINOR: contrib/prometheus-exporter: add recv logs_logs_total field

this field was added by commit 45c457a62941a7c4a86ce4327d7755edcd4b230e
("MINOR: log: adds counters on received syslog messages.")

Signed-off-by: William Dauchy <wdauchy@gmail.com>
diff --git a/contrib/prometheus-exporter/service-prometheus.c b/contrib/prometheus-exporter/service-prometheus.c
index debe2f6..e62ad94 100644
--- a/contrib/prometheus-exporter/service-prometheus.c
+++ b/contrib/prometheus-exporter/service-prometheus.c
@@ -177,6 +177,7 @@
 	[INF_TOTAL_SPLICED_BYTES_OUT]        = { .n = IST("spliced_bytes_out_total"),       .type = PROMEX_MT_COUNTER, .flags = PROMEX_FL_INFO_METRIC },
 	[INF_BYTES_OUT_RATE]                 = { .n = IST("bytes_out_rate"),                .type = PROMEX_MT_GAUGE,   .flags = PROMEX_FL_INFO_METRIC },
 	//[INF_DEBUG_COMMANDS_ISSUED]          ignored
+	[INF_CUM_LOG_MSGS]                   = { .n = IST("recv_logs_total"),               .type = PROMEX_MT_COUNTER, .flags = PROMEX_FL_INFO_METRIC },
 };
 
 /* frontend/backend/server fields */