MINOR: stats: support clear counters for dynamic stats

Add a boolean 'clearable' on stats module structure. If set, it forces
all the counters to be reset on 'clear counters' cli command. If not,
the counters are reset only when 'clear counters all' is used.
diff --git a/include/haproxy/stats-t.h b/include/haproxy/stats-t.h
index 3be2b4a..96dcf18 100644
--- a/include/haproxy/stats-t.h
+++ b/include/haproxy/stats-t.h
@@ -477,6 +477,7 @@
 	size_t counters_size;    /* sizeof counters */
 
 	uint32_t domain_flags;   /* stats application domain for this module */
+	char clearable;          /* reset on a clear counters */
 };
 
 struct extra_counters {
diff --git a/src/stats.c b/src/stats.c
index 12b5945..2042687 100644
--- a/src/stats.c
+++ b/src/stats.c
@@ -3963,6 +3963,7 @@
 	struct proxy *px;
 	struct server *sv;
 	struct listener *li;
+	struct stats_module *mod;
 	int clrall = 0;
 
 	if (strcmp(args[2], "all") == 0)
@@ -4023,6 +4024,47 @@
 	global.ssl_fe_keys_max = 0;
 	global.ssl_be_keys_max = 0;
 
+	list_for_each_entry(mod, &stats_module_list[STATS_DOMAIN_PROXY], list) {
+		if (!mod->clearable && !clrall)
+			continue;
+
+		for (px = proxies_list; px; px = px->next) {
+			enum stats_domain_px_cap mod_cap = stats_px_get_cap(mod->domain_flags);
+
+			if (px->cap & PR_CAP_FE && mod_cap & STATS_PX_CAP_FE) {
+				EXTRA_COUNTERS_INIT(px->extra_counters_fe,
+				                    mod,
+				                    mod->counters,
+				                    mod->counters_size);
+			}
+
+			if (px->cap & PR_CAP_BE && mod_cap & STATS_PX_CAP_BE) {
+				EXTRA_COUNTERS_INIT(px->extra_counters_be,
+				                    mod,
+				                    mod->counters,
+				                    mod->counters_size);
+			}
+
+			if (mod_cap & STATS_PX_CAP_SRV) {
+				for (sv = px->srv; sv; sv = sv->next) {
+					EXTRA_COUNTERS_INIT(sv->extra_counters,
+				                            mod,
+					                    mod->counters,
+					                    mod->counters_size);
+				}
+			}
+
+			if (mod_cap & STATS_PX_CAP_LI) {
+				list_for_each_entry(li, &px->conf.listeners, by_fe) {
+					EXTRA_COUNTERS_INIT(li->extra_counters,
+				                            mod,
+					                    mod->counters,
+					                    mod->counters_size);
+				}
+			}
+		}
+	}
+
 	memset(activity, 0, sizeof(activity));
 	return 1;
 }