The class org.hibernate.osgi.HibernateBundleActivator export HibernateBundleActivator as persistence provider class whereas it should export org.hibernate.jpa.HibernatePersistenceProvider

Now:
properties.put(
"javax.persistence.provider",
HibernateBundleActivator.class.getName() );

Should be:
properties.put(
"javax.persistence.provider",
HibernatePersistenceProvider.class.getName() );

Unless I missing something.