Currently the flavor creation form always check for the uniqueness
of the UUID field, even when it is set to "auto". That means that if
we create a flavor with UUID value of "auto", the check will fail.
This patch disable the check when UUID is automatically generated.
Change-Id: Ie31307d67cf3857e3bb80c124e92c81e0c6a2982
af7e6c4f75