Bug 33483: Prevent 400 when more than 1 agreement is linked

Bug 33483: Prevent 400 when more than 1 agreement is linked

We were passing package_agreements.agreement and the server returned
Object { message: "Properties not allowed: agreement.", path: "/body/package_agreements/0" }

Signed-off-by: Pedro Amorim <pedro.amorim@ptfs-europe.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
(cherry picked from commit bb30aab206e218946fa3fe5104850a1d79553ac6)
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>