Never thought of it as a shanty, myself, but could see the resemblence to some shanties now it is pointed out.

I learned the chorus as:

Johnny is a drinkin'roving blade, Johnny is a roving blade Johnny is a drinkin'roving blade, Johnny is a roving blade

and I've also heard it done as "blinkin' roving" and "stinkin' roving"

MMario