fix the issue which causes keystone authentication context has been igorned

Signed-off-by: ywang19 <yaguang.wang@intel.com>

Author: ywang19

dev/cosbench-driver/src/com/intel/cosbench/driver/agent/AuthAgent.java

@@ -74,8 +74,7 @@ protected void execute() {
     private AuthContext login() {
         Logger logger = getMissionLogger();
         AuthAPI authApi = workerContext.getAuthApi();
-        if(authApi instanceof NoneAuth) // bypass caching handling for NoneAuth.
-        	return null;
+
         int attempts = 0;
         while (attempts++ < loginAttempts - 1)
             try {