improve handling of subclasses of Spring transaction manager in SingleSessionCommandService.initTransactionManager(..)

SingleSessionCommandService.initTransactionManager(..) checks the transaction manager that is passed in to see if it is from the Spring Framework:

if ( tm != null && tm.getClass().getName().startsWith( "org.springframework" ) ) {

By checking the class by name, it misses the case of a subclass of a Spring transaction manager (e.g. org.codehaus.groovy.grails.orm.hibernate.GrailsHibernateTransactionManager which extends org.springframework.orm.hibernate3.HibernateTransactionManager.)

It would have saved me some headache and it will save me a few lines of code if this code checks superclasses as well.