fixes #6550 / BZ 1117952 - fix issues with changing org name which affected running db:seed

Without these changes, the user cannot change the default organization
name and re-run 'rake db:seed'.  The reason being, it would attempt
to create an organization with a label that was already in use and
the seed would fail.

In order to address this, this commit does a couple of things:
1. when creating an org, if a label is automatically generated
   and it is already in use, re-generate the label using a uuid.
2. fix an existing validation which was incorrectly comparing
   name=label, label=name, etc. during org create and update.
@ehelms, Agreed.  The user interaction for handling the label on the organization page is not ideal.  We have an existing issue to improve that.  The issue is : http://projects.theforeman.org/issues/5953 .

Assuming that we use an approach similar to what is used on other pages (e.g. products), this will no longer be an issue.  In those cases, the auto-generation of the label is performed client-side.  So, when the create is sent to the server, it will have a value.  If that value conflicts with an existing label, the user gets a validation error and has an opportunity to change & resubmit.