bump up httpclient version

Author: zoewangg

pom.xml

@@ -145,7 +145,7 @@
         <aspectj.version>1.8.2</aspectj.version>
 
         <jre.version>1.8</jre.version>
-        <httpcomponents.httpclient.version>4.5.8</httpcomponents.httpclient.version>
+        <httpcomponents.httpclient.version>4.5.9</httpcomponents.httpclient.version>
         <httpcomponents.httpcore.version>4.4.10</httpcomponents.httpcore.version>
 
         <!-- These properties are used by cucumber tests related code -->