AM V3 reports incorrect error when no local resources exist for the aggregate.

[lnevers@bbn.com]

In a scenario where the AM API V3 aggregate is queried for a slice which has no resources local to the aggregate, the incorrect error is returned.

Here is the sequence that show the error:

1. Create a slice: ($omni.py createslice lnv3)
2. Describe the slice, which has no resources at the V3 aggregate:

   $ omni.py describe lnv3  -a ig-gpo
   INFO:omni:Loading config file /home/lnevers/.gcf/omni_config
   INFO:omni:Using control framework pg
   INFO:omni:Substituting AM nickname ig-gpo with URL http://instageni.gpolab.bbn.com/protogeni/xmlrpc/am/2.0, URN unspecified_AM_URN
   ERROR:omni:Describe is only available in AM API v3+. Use ListResources with AM API v2, or specify -V3 to use AM API v3.
   lnevers@arendia:~/gcf-2.2-rc3$ omni.py describe lnv3  -a ig-gpo3 -V3
   INFO:omni:Loading config file /home/lnevers/.gcf/omni_config
   INFO:omni:Using control framework pg
   INFO:omni:Substituting AM nickname ig-gpo3 with URL http://instageni.gpolab.bbn.com/protogeni/xmlrpc/am/3.0, URN unspecified_AM_URN
   INFO:omni:Slice urn:publicid:IDN+pgeni.gpolab.bbn.com+slice+lnv3 expires on 2013-01-08 18:26:11 UTC
   INFO:omni:Substituting AM nickname ig-gpo3 with URL http://instageni.gpolab.bbn.com/protogeni/xmlrpc/am/3.0, URN unspecified_AM_URN
   INFO:omni:Describe Slice urn:publicid:IDN+pgeni.gpolab.bbn.com+slice+lnv3:
   WARNING:omni:Got no resource listing from AM http://instageni.gpolab.bbn.com/protogeni/xmlrpc/am/3.0
   INFO:omni: ------------------------------------------------------------
   INFO:omni: Completed describe:
   
     Options as run:
   		aggregate: ['ig-gpo3']
   		api_version: 3
   		framework: pg
   
     Args: describe lnv3
   
     Result Summary: Slice urn:publicid:IDN+pgeni.gpolab.bbn.com+slice+lnv3 expires on 2013-01-08 18:26:11 UTC
   
   Failed to Describe slice urn:publicid:IDN+pgeni.gpolab.bbn.com+slice+lnv3 at AM http://instageni.gpolab.bbn.com/protogeni/xmlrpc/am/3.0: Error from Aggregate: code 7. protogeni AM code: 7: Slice credential not provided (PG error log: urn:publicid:IDN+instageni.gpolab.bbn.com+log+13209).
   Found description of slivers on 0 of 1 possible aggregates. 
   INFO:omni: ============================================================
   

The error is for slice credential, which is not the proper reason for this failure. Error needs to reflect that the aggregate has no resources for the requested slice.

[lnevers@bbn.com]

No change in this AM API V3 issue. When the slice has no resources, the error reports that bad credentials are used rather than no resources exist.