dscache: Reduce log level of memcache failures.

filter/dscache/support.go

Index: filter/dscache/support.go
diff --git a/filter/dscache/support.go b/filter/dscache/support.go
index a472a8ba64d1e0b784553c8151afb612bf93a34e..edcd967ef58731a7a3932264c5aff3ef0169531d 100644
--- a/filter/dscache/support.go
+++ b/filter/dscache/support.go
@@ -119,7 +119,7 @@ func (s *supportContext) mutation(keys []*ds.Key, f func() error) error {
 	err := f()
 	if err == nil {
 		if err := errors.Filter(s.mc.DeleteMulti(lockKeys), memcache.ErrCacheMiss); err != nil {
-			(log.Fields{log.ErrorKey: err}).Warningf(
+			(log.Fields{log.ErrorKey: err}).Debugf(
 				s.c, "dscache: mc.DeleteMulti")
 		}
 	}