drmtest: don't leak memory when parsing the arguments
drmtest: don't leak memory when parsing the arguments

Found this while investigating memory leaks on kms_flip. Detected by
Valgrind.

Signed-off-by: Paulo Zanoni <cc0e04a2103c45cd195651d976f79813d0f66bdf@intel.com>

yipdw/intel-gpu-tools,tiagovignatti/intel-gpu-tools,tiagovignatti/intel-gpu-tools,rib/intel-gpu-tools,tiagovignatti/intel-gpu-tools,erikarn/intel-gpu-tools,mv0/intel-gpu-tools,chenxianqin/intel-gpu-tools,erikarn/intel-gpu-tools,dlespiau/checkmate-test-igt,chenxianqin/intel-gpu-tools,yipdw/intel-gpu-tools,erikarn/intel-gpu-tools,dlespiau/checkmate-test-igt,chenxianqin/intel-gpu-tools,tiagovignatti/intel-gpu-tools,mv0/intel-gpu-tools,rib/intel-gpu-tools,erikarn/intel-gpu-tools,mv0/intel-gpu-tools,yipdw/intel-gpu-tools,rib/intel-gpu-tools,rib/intel-gpu-tools,dlespiau/checkmate-test-igt,mv0/intel-gpu-tools,yipdw/intel-gpu-tools,dlespiau/checkmate-test-igt,chenxianqin/intel-gpu-tools