knocking sound from front end, goes away as soon as i touch the brake pedal

I just had new pads and rotors installed on my 2006 TRD Sport. When I'm driving between about 10 and 60 mph I can hear a knocking sound from my front end. It speeds up and slows down based on my speed. As soon as I apply the brakes, even a little, it goes away. Could something be loose in my brake calipers? I took my driver's side front wheel off and inspected the brakes. There seems to be some play in the pads and also the pins that hold that pads in. I'm not sure how much play, if any, is considered normal. An experienced mechanic did the brakes for me. He's out of town for a week, so I'm trying to figure it out on my own. Has anyone else had a similar issue? Thanks for any advice you have.

 

Did he use OEM Pads or aftermarket?

Probably just the pads shifting around on the pins.

 

Perhaps a piston seized in the caliper. The pads should not be banging around

 

Does it pull to one side? If so a seized piston is a possibility. The Tacoma's are known to have the pads move around when changing from reverse to forward. Common, but it doesn't effect anything.