MINOR: stats: Expose native cum_req metric for a server

Expose native cum_req metric for a server: so far it was calculated as a
sum or all responses. Rename it from Cum. HTTP Responses to Cum. HTTP
Requests to be consistent with Frontend and Backend.
diff --git a/contrib/prometheus-exporter/service-prometheus.c b/contrib/prometheus-exporter/service-prometheus.c
index 54770ef..f7542d2 100644
--- a/contrib/prometheus-exporter/service-prometheus.c
+++ b/contrib/prometheus-exporter/service-prometheus.c
@@ -2061,6 +2061,11 @@
 					case ST_F_LBTOT:
 						metric = mkf_u64(FN_COUNTER, sv->counters.cum_lbconn);
 						break;
+					case ST_F_REQ_TOT:
+						if (px->mode != PR_MODE_HTTP)
+							goto next_px;
+						metric = mkf_u64(FN_COUNTER, sv->counters.p.http.cum_req);
+						break;
 					case ST_F_HRSP_1XX:
 						if (px->mode != PR_MODE_HTTP)
 							goto next_px;