Do not report for ENOENT for the cookie file.

This now causes a string of error messages, because our cookie update
process does multiple file operations before finally installing the
cookie file.

Change-Id: Iebcff0f8809956960da02b9cbd780d00975d8db9

cookie/cookie.go

diff --git a/cookie/cookie.go b/cookie/cookie.go
index cdb6282..ca2df64 100644
--- a/cookie/cookie.go
+++ b/cookie/cookie.go
@@ -97,6 +97,10 @@
 			select {
 			case <-w.Events:
 				fi, err := os.Stat(path)
+				if os.IsNotExist(err) {
+					continue
+				}
+
 				if err != nil {
 					log.Printf("Stat(%s): %v", path, err)
 					continue