Meaning of "A man has as many masters as he has vices."

Solution 1:

He's paraphrasing his Boss:

John 8:34

Everyone who commits sin is a slave of sin.

Solution 2:

It means your vices control you; they are your masters.

While you may think you are your own master, or that you serve one master, in reality, the things you are addicted to control your behavior, and, therefore, you.