Substitute deprecated method call in HibernateContextDAO and added unit test

https://tickets.openmrs.org/browse/TRUNK-4140

Removed deprecated method call.
Added a unit test. But the unit test fails. It throws a java.util.concurrentmodificationexception. Perhaps it could be a problem in HibernateContextDAO.mergeDefaultRuntimeProperties(Properties runtimeProperties) method. can you please check this?