Synchronize isAPIThrottled method to handle concurrency issues

Author: msm1992

components/apimgt/org.wso2.carbon.apimgt.gateway/src/main/java/org/wso2/carbon/apimgt/gateway/throttling/ThrottleDataHolder.java

@@ -122,20 +122,19 @@ public void removeThrottledAPIKey(String key){
         throttledAPIKeysMap.remove(key);
     }
 
-    public boolean isAPIThrottled(String apiKey){
-        boolean isThrottled = this.throttledAPIKeysMap.containsKey(apiKey);
-        if(isThrottled) {
+    public boolean isAPIThrottled(String apiKey) {
+        Long timestamp = this.throttledAPIKeysMap.get(apiKey);
+        if (timestamp != null) {
             long currentTime = System.currentTimeMillis();
-            long timestamp = this.throttledAPIKeysMap.get(apiKey);
-            if(timestamp >= currentTime) {
-                return isThrottled;
+            if (timestamp >= currentTime) {
+                return true;
             } else {
                 this.throttledAPIKeysMap.remove(apiKey);
                 this.conditionDtoMap.remove(apiKey);
                 return false;
             }
         } else {
-            return isThrottled;
+            return false;
         }
     }