scripts: sanitylib.py: enhancement for QEMUHandler

Sometimes QEMU can't handle SIGTERM signal correctly and just
run as normal, in that case kill -9 QEMU process directly and
leave sanitycheck judge the testing result by console output.

For failures caused by other reasons, terminate all releated
processes to avoid CI waits 2 hours and reports timeout.

Signed-off-by: Wentong Wu <wentong.wu@intel.com>