Fix `make check` pylint errors
Fix `make check` pylint errors

Caused by a combination of factors: the new code from dd44303b (Load
templatematch parameters' default values from stbt.conf) being rebased
after 1276c4e3 (Enable pylint warnings and style checks).

The errors were:

stbt.py:1259: [W0601] Global variable 'load_config' undefined at the module level
stbt.py:1262: [W0613] Unused argument 'tool'

stb-tester/stb-tester,wmanley/stb-tester,martynjarvis/stb-tester,wmanley/stb-tester,martynjarvis/stb-tester,stb-tester/stb-tester,wmanley/stb-tester,LewisHaley/stb-tester,martynjarvis/stb-tester,martynjarvis/stb-tester,LewisHaley/stb-tester,martynjarvis/stb-tester,LewisHaley/stb-tester,stb-tester/stb-tester,wmanley/stb-tester,martynjarvis/stb-tester,LewisHaley/stb-tester,stb-tester/stb-tester,LewisHaley/stb-tester,martynjarvis/stb-tester,LewisHaley/stb-tester,wmanley/stb-tester,LewisHaley/stb-tester