Description of problem:
content host id and uuid are both used as content host identifiers, what is quite confusing

Version-Release number of selected component (if applicable):
Satellite-6.0.4-RHEL-6-20140716.0-Satellite-x86_64

How reproducible:
always

Steps to Reproduce:
1. Compare various content host identifiers

Actual results:
1. hammer interprets uuid as id
# hammer content-host list --organization-id 1
-------------------------------------|-----------------------------------
ID                                   | NAME                              
-------------------------------------|-----------------------------------
49eb6336-03cf-4396-8302-67d3cff2c24e | vmware194.englab.brq.redhat.com   
...

2. api documentation for "PUT /katello/api/systems/:id" says:
id /required/ UUID of the content host /Value: String

so, uuid is used as content host id

3. but the return hash of "PUT /katello/api/systems/:id" API with 'id' set to 'b7dbf416-dd8d-4ab5-95ed-ffe51100ce2c' contains:
{..., "id"=>2, ...}
it contains uuid as well: "uuid"=>"b7dbf416-dd8d-4ab5-95ed-ffe51100ce2c",
but it's confusing to update an object with a specific *id* and getting another *id* in the response

Expected results:
Hide the 'real' content host id ("id"=>2) from the user as it isn't used anywhere and is only confusing (or drop it completely)

Additional info:
What about returning both - id and uuid keys - with the same value?
{..., "id"=>"b7dbf416-dd8d-4ab5-95ed-ffe51100ce2c", "uuid"=>"b7dbf416-dd8d-4ab5-95ed-ffe51100ce2c", ...}