Create test case for MODE-2122 demonstrating failed persistence of generated namespaces

This test fails with the exception:

```
javax.jcr.NamespaceException: There is no namespace with URI "info:a#"
	at org.modeshape.jcr.JcrNamespaceRegistry.getPrefix(JcrNamespaceRegistry.java:153)
	at org.modeshape.jcr.RepositoryPersistenceTest$2.call(RepositoryPersistenceTest.java:110)
```