cubicweb-mercurial-server #3252322 avoid ssh prompts [validation pending]

prioritynormal
typebug
done in0.4.0
load0.500
load left0.000
closed by#bd59932b2ee0 [utils] tell ssh and hg to not prompt in mscui (closes #3252322)
patch[utils] tell ssh and hg to not prompt in mscui [applied]