Ignore *.pk droppings from the Dummy switch driver

Change-Id: Ife8e918f8d1222ec3a8e32d7d3632a50ce4c0dd6
diff --git a/.gitignore b/.gitignore
index 1699fa3..0f74688 100644
--- a/.gitignore
+++ b/.gitignore
@@ -15,3 +15,4 @@
 .idea
 *.egg-info
 *.log
+*.pk