Nodes roles should be checked in CheckBeforeDeploymentTask,
because it's possible to deploy node with conflicting roles
or with incompatible role. Roles release metadata will be
used for roles checks, this metadata contains restrictions.
Since `depends` is not used anymore, it's changed to
`restrictions` in assignment validator.
Change-Id: Ibba7951968cbafd59fff0d516e74f9dd9e454edc
Closes-Bug: #1573006
93d7fb982b