Withdrawing from PhD with or without a Master Degree
It's quite common for people to leave a Ph.D. program. In my experience, employers don't really see that as a negative; people leave for many reasons, and they'll likely rather focus on whether or not you learned anything while you were there that will help you do the job they're interviewing you for.

It sounds like you have a time-investment vs. reward tradeoff to consider here. A summer is not that long, but you may have to make some sacrifices in order to free up that time. A second MS in the same discipline is not going to help you very much at all, especially in industry jobs, unless there's something significant about it that makes it stand out (is it a thesis-based MS vs. a class-hours based MS, or perhaps it's slightly different but the difference in topic is something employers will respond to). 

If you can delay a job search for the summer to get the second MS, and you'd like to cash out the "sweat equity" you've accumulated in your current program by getting a degree for it, then I don't think there's a big problem with doing that. If you didn't already have an MS, I'd say definitely get this one, but that's not your case. Just keep in mind that getting the additional MS is unlikely to open doors any wider for you, and not getting it is unlikely to close them.