restapi: allow no QoS for Profile element

When there's no qos for profile, the generated profile
doesn't contain is, so minOccurs of qos ref should be 0.

Change-Id: I6262103d38376003ffe1b98d17400eaf5c5e387b
Bug-Url: https://bugzilla.redhat.com/1135761
Signed-off-by: Gilad Chaplik <gchaplik@redhat.com>