first, drug dogs dont sniff for drugs unless ordered to by their handlers... but their entire job is to smell for drugs when ordered to do so.. so yea.. they can smell a grow op if they are ordered...
secondly if you have done your job sealing up your grow you dont have anything to worry about.. that means a working filter, all air leaving the grow room is "scrubbed clean", and you dont have something like a window open or something stupid in the room that would allow the smell to travel...
but, hypothetically speaking, if your filter wasnt working properly, and you had a leak, and the police happened to be in the area, and just happened to walk by your place, and the dog just happened to catch a wiff, it is possible he could signal it to the officer and they could investigate.. but seeings as most of that is hypothetical your fine...