Fix for NMS-6389: vmwarereqtool is initializing the DB Pool

VmwareViJavaAccess forces the initialization of all the Spring context
if the class is instantiated without user credentials, in order to
retrieve the implementation of VmwareConfigDao.

VmwareRequisitionTool was refactored to parse and retrieve the
credentials from vmware-config.xml if the URL doesn't contain the
credentials.