AdbDevice.get_frame: Only retry 3 times
AdbDevice.get_frame: Only retry 3 times

This symptom (it got a png from adb but the png was corrupt) only
happened 1 time in a 10-hour soak. Retrying 10 times seems excessive.

stb-tester/stb-tester,LewisHaley/stb-tester,LewisHaley/stb-tester,LewisHaley/stb-tester,stb-tester/stb-tester,LewisHaley/stb-tester,stb-tester/stb-tester,LewisHaley/stb-tester,LewisHaley/stb-tester,stb-tester/stb-tester,LewisHaley/stb-tester