PYTHON-2608 Kill background KMS servers at exit

Author: ShaneHarvey

.evergreen/run-tests.sh

@@ -150,6 +150,7 @@ if [ -n "$TEST_ENCRYPTION" ]; then
         pushd ${DRIVERS_TOOLS}/.evergreen/csfle
         python -u lib/kms_http_server.py --ca_file ../x509gen/ca.pem --cert_file ../x509gen/expired.pem --port 8000 &
         python -u lib/kms_http_server.py --ca_file ../x509gen/ca.pem --cert_file ../x509gen/wrong-host.pem --port 8001 &
+        trap 'kill $(jobs -p)' EXIT HUP
         popd
     fi
 fi