Currently if an admin tries to create a trusted queue, Neutron will
fail with MissingDSCPForTrusted exception. However, the NVP semantic
is exactly the opposite, namely the DSCP field must be specified for
untrusted queues and omitted trusted ones.
Fixes bug #1204256
Change-Id: I935fab45fc811a296411283a641b66c5ca96264d