Add missing signal import

Change-Id: I89d8510dac0697de0fe503c242381b8981286114
diff --git a/docker_entrypoint/monitoring/__init__.py b/docker_entrypoint/monitoring/__init__.py
index d4fa98f..c02a5ac 100644
--- a/docker_entrypoint/monitoring/__init__.py
+++ b/docker_entrypoint/monitoring/__init__.py
@@ -6,6 +6,7 @@
 import logging
 import os
 import pwd
+import signal
 import subprocess
 import sys
 import time