test/nvme: kill stub with -9 when a failure occurs

This ensures the stub gets killed so that we can
make forward progress on collecting a backtrace.

This requires adding an optional parameter to the
kill_stub function to specify a signal.

Signed-off-by: Jim Harris <james.r.harris@intel.com>
Change-Id: Ib46d07b6651c6f35382f38c97901def03f28289d

Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/452891
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-by: Shuhei Matsumoto <shuhei.matsumoto.xt@hitachi.com>
Reviewed-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>

test/common/autotest_common.sh

@@ -506,7 +506,7 @@ function start_stub() {
 }
 
 function kill_stub() {
-	kill $stubpid
+	kill $1 $stubpid
 	wait $stubpid
 	rm -f /var/run/spdk_stub0
 	# Re-enable ASLR now that we are done with multi-process testing

test/nvme/nvme.sh

@@ -89,7 +89,7 @@ fi
 
 if [ `uname` = Linux ]; then
 	start_stub "-s 4096 -i 0 -m 0xF"
-	trap "kill_stub; exit 1" SIGINT SIGTERM EXIT
+	trap "kill_stub -9; exit 1" SIGINT SIGTERM EXIT
 fi
 
 if [ $RUN_NIGHTLY -eq 1 ]; then