1093760 - pulp-manage-db now halts if a migration fails

https://bugzilla.redhat.com/show_bug.cgi?id=1093760

Output now looks something like
```
Loading content types.
Content types loaded.
Ensuring the admin role and user are in place.
Admin role and user are in place.
Beginning database migrations.
Applying pulp.server.db.migrations version 9
Applying migration pulp.server.db.migrations.0009_qpid_queues failed.

Halting migrations due to a migration failure.  See log for details.
[Errno 111] Connection refused
[jcline@jcline pulp]$ 
```