MINOR: stats: add server revision id support

Make use of the new srv->rid value in stats.

Stat is referred as ST_F_SRID, it is now used in stats_fill_sv_stats
function in order to be included in csv and json stats dumps.

Moreover, "rid: $value" will be displayed next to server puid
in html stats page if "stats show-legend" is specified in the stats frontend.
(mouse hovering tooltip)

Depends on the following commit:
	"MINOR: server: add srv->rid (revision id) value"
diff --git a/include/haproxy/stats-t.h b/include/haproxy/stats-t.h
index efa0ac3..1a7d3d1 100644
--- a/include/haproxy/stats-t.h
+++ b/include/haproxy/stats-t.h
@@ -456,6 +456,7 @@
 	ST_F_NEED_CONN_EST,
 	ST_F_UWEIGHT,
 	ST_F_AGG_SRV_CHECK_STATUS,
+	ST_F_SRID,
 
 	/* must always be the last one */
 	ST_F_TOTAL_FIELDS
diff --git a/src/stats.c b/src/stats.c
index 8ed5a71..5fd4d3f 100644
--- a/src/stats.c
+++ b/src/stats.c
@@ -260,6 +260,7 @@
 	[ST_F_NEED_CONN_EST]                 = { .name = "need_conn_est",               .desc = "Estimated needed number of connections"},
 	[ST_F_UWEIGHT]                       = { .name = "uweight",                     .desc = "Server's user weight, or sum of active servers' user weights for a backend" },
 	[ST_F_AGG_SRV_CHECK_STATUS]          = { .name = "agg_server_check_status",     .desc = "Backend's aggregated gauge of servers' state check status" },
+	[ST_F_SRID]                          = { .name = "srid",                        .desc = "Server id revision, to prevent server id reuse mixups" },
 };
 
 /* one line of info */
@@ -1153,7 +1154,7 @@
 				chunk_appendf(out, "%s, ", field_str(stats, ST_F_ADDR));
 
 			/* id */
-			chunk_appendf(out, "id: %d", stats[ST_F_SID].u.u32);
+			chunk_appendf(out, "id: %d, rid: %d", stats[ST_F_SID].u.u32, stats[ST_F_SRID].u.u32);
 
 			/* cookie */
 			if (stats[ST_F_COOKIE].type) {
@@ -2283,6 +2284,9 @@
 			case ST_F_SID:
 				metric = mkf_u32(FO_KEY|FS_SERVICE, sv->puid);
 				break;
+			case ST_F_SRID:
+				metric = mkf_u32(FN_COUNTER, sv->rid);
+				break;
 			case ST_F_THROTTLE:
 				if (sv->cur_state == SRV_ST_STARTING && !server_is_draining(sv))
 					metric = mkf_u32(FN_AVG, server_throttle_rate(sv));