If an ueber certificate exists for an Owner when a manifest import is undone, the ueber certifcate will be deleted. This will leave the ueber data in a bad state and will break the GET /owners/:owner_key/uebercert API.


Steps to Reproduce:
1. Create a new owner.

2. Import a manifest for that owner.

3. Generate an ueber certificate for that owner.
curl -k -u admin:admin -X POST https://localhost:8443/candlepin/owners/:owner_key/uebercert

4. Undo the manifest that was imported.
curl -k -u admin:admin -X DELETE https://localhost:8443/candlepin/owners/:owner_key/imports

5. Fetch the ueber cert for the owner.
curl -k -u admin:admin https://localhost:8443/candlepin/owners/:owner_key/uebercert



Actual results:

2017-02-08 13:02:22,308 [thread=http-nio-8443-exec-3] [req=4b76a72e-e753-4952-aefe-b2419fa50e03, org=] INFO  org.candlepin.common.filter.LoggingFilter - Request: verb=GET, uri=/candlepin/owners/defaultorg/uebercert
2017-02-08 13:02:22,355 [thread=http-nio-8443-exec-3] [req=4b76a72e-e753-4952-aefe-b2419fa50e03, org=defaultorg] ERROR org.candlepin.common.exceptions.mappers.CandlepinExceptionMapper - Runtime Error Index: 0, Size: 0 at java.util.ArrayList.rangeCheck:653
java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
	at java.util.ArrayList.rangeCheck(ArrayList.java:653) ~[na:1.8.0_111]
	at java.util.ArrayList.get(ArrayList.java:429) ~[na:1.8.0_111]
	at org.candlepin.resource.OwnerResource.getUeberCertificate(OwnerResource.java:1440) ~[classes/:]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_111]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_111]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_111]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_111]


Expected results:
An appropriate ueber certificate should be returned by the ueber cert API after the manifest is removed.