Re-add pid file

adsms.py

@@ -83,4 +83,13 @@ if __name__ == "__main__":
     args = parser.parse_args()
 
     config = load_config(args.config_file)
-    run(config)
+
+    try:
+        if config["pid_file"]:
+            with open(config["pid_file"], "w+") as f:
+                f.write(str(os.getpid()))
+
+        run(config)
+    finally:
+        if config["pid_file"]:
+            os.unlink(config["pid_file"])