Restrict slaves used by itests

Currently, when nuxeo-studio-master passes it triggers a bench of nuxeo-studio-master-itests* jobs which can occupate all available slaves for a short while.

They should avoid to run on special slave dedicated to more urgent jobs such as release (i.e. smeagol).

The new tag *PRIV_DEPLOY * has been added to smeagol to differenciate it form others.

Let's tell these jobs to do not run on such slave.

Moreover, in perspective of the fusion of qa and qapriv, all slaves dedicated to private build will have the SLAVEPRIV label. This SLAVEPRIV is already added on current qapriv slaves.

So the label expression to be used is SLAVEPRIV&&!PRIV_DEPLOY and it will be compatible with the future qa/qapriv fusion.