Add setter for connectionPoolCleanerPeriod in AsyncHttpClient Builder

Author: agapic

client/src/main/java/org/asynchttpclient/DefaultAsyncHttpClientConfig.java

@@ -949,6 +949,11 @@ public Builder setPooledConnectionIdleTimeout(int pooledConnectionIdleTimeout) {
       return this;
     }
 
+    public Builder setConnectionPoolCleanerPeriod(int connectionPoolCleanerPeriod) {
+      this.connectionPoolCleanerPeriod = connectionPoolCleanerPeriod;
+      return this;
+    }
+
     public Builder setConnectionTtl(int connectionTtl) {
       this.connectionTtl = connectionTtl;
       return this;