Test case for MODE-2122

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)
```

(Targeted against 3.x, I'll verify it's still a problem on master shortly.)