Update `DataSourceInitializedPublisher` to fallback to the
`LocalContainerEntityManagerFactoryBean` if the
`javax.persistence.nonJtaDataSource` property is not defined.

As of Hibernate 4.3 the property is no longer set if the `EntityManager`
is created from a `PersistenceUnitInfo` instance rather than actual
properties.

Although this is being addressed in Hibernate issue HHH-13432, it's
not strictly a requirement of the JPA spec that the property is set.

Fixes gh-17061