restapi: allow no parent element for Profile

Since profile is used as a ref in VM/Template or disk,
we need to allow no inner elements within profile.

Change-Id: I1ae61a0815fa66d907ee65eda274a76b036b9023
Bug-Url: https://bugzilla.redhat.com/1135761
Signed-off-by: Gilad Chaplik <gchaplik@redhat.com>