stbt-lint tests: Ignore "Using config file..." from pylint 1.8
stbt-lint tests: Ignore "Using config file..." from pylint 1.8

Pylint 1.8 prints "Using config file <path to pylint.conf>", but
pylint 1.5 doesn't.

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