HdmiCecControl: Fix for Python 3
HdmiCecControl: Fix for Python 3

tested ok on Python 2.7 in Ubuntu 18 and Python 3.8 in Ubuntu 20

Fixes #673.

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