Fixed wrong xml type name

pdp-testutils/src/test/resources/org/ow2/authzforce/core/pdp/testutil/test/pdp.xml

 <?xml version="1.0" encoding="UTF-8"?>
 <!-- Testing parameter 'maxPolicySetRefDepth' -->
 <pdp xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://authzforce.github.io/core/xmlns/pdp/6.0" xmlns:ext="http://authzforce.github.io/core/xmlns/test/3" version="6.0.0">
-   <refPolicyProvider id="refPolicyProvider" xsi:type="ext:MongoDBBasedPolicyProvider" serverHost="localhost" serverPort="27017" dbName="Test" collectionName="policies" />
+   <refPolicyProvider id="refPolicyProvider" xsi:type="ext:MongoDBBasedPolicyProviderDescriptor" serverHost="localhost" serverPort="27017" dbName="Test" collectionName="policies" />
    <rootPolicyProvider id="rootPolicyProvider" xsi:type="StaticRefBasedRootPolicyProvider">
       <policyRef>root-rbac-policyset</policyRef>
    </rootPolicyProvider>
 
-</pdp>
\ No newline at end of file
+</pdp>