docs: XMLRPC API docs for jobs.set_response

Bug: 1127509
Change-Id: I26d5e834115e3c0cde0b1a07a3ab3035c9462bb0
docs: expand description of recipe set ack/nak

Bug: 1127509
Change-Id: I4bc3e507fa48e0e4839eff896fe0a238104c60ec