Offboard control fix

We we're having some issues with offboard setpoint control and eventually tracked it down to here.  The code was ignoring yaw and yaw rate masks due to improper bit shifting.  

Navigator was also repeatedly publishing invalid setpoints, which would drown out valid setpoints coming via mavlink.

I'm not sure if these fixes align with best practices - I'll let someone else be the judge of that.  

In any case, this fixed our issues and hopefully this helps someone else.  
This looks like the proper fix. The only preference I have there is to do this as a class variable instead, since static variables are pitfalls in case of multiple instances of the same class. It also seems like the state should be reset whenever a valid SP is published again.