fix lalb be disabled wrongly

src/brpc/policy/locality_aware_load_balancer.cpp

@@ -555,7 +555,7 @@ LocalityAwareLoadBalancer::Weight::~Weight() {
 int64_t LocalityAwareLoadBalancer::Weight::Disable() {
     BAIDU_SCOPED_LOCK(_mutex);
     const int64_t saved = _weight;
-    _base_weight = 0;
+    _base_weight = -1;
     _weight = 0;
     return saved;
 }

src/brpc/policy/locality_aware_load_balancer.h

@@ -86,7 +86,7 @@ private:
         void Describe(std::ostream& os, int64_t now);
 
         int64_t Disable();
-        bool Disabled() const { return _base_weight == 0; }
+        bool Disabled() const { return _base_weight == -1; }
         int64_t MarkOld(size_t index);
         std::pair<int64_t, int64_t> ClearOld();