Drop RecurringPurge.

It had a race condition. Removing it frees us from having go-routines
hanging around after the FS is unmounted.

unionfs/timedcache.go

@@ -96,16 +96,6 @@ func (c *TimedCache) Purge() {
 	}
 }
 
-func (c *TimedCache) RecurringPurge() {
-	if c.ttl <= 0 {
-		return
-	}
-
-	c.Purge()
-	c.PurgeTimer = time.AfterFunc(c.ttl*5,
-		func() { c.RecurringPurge() })
-}
-
 func (c *TimedCache) DropAll(names []string) {
 	c.cacheMapMutex.Lock()
 	defer c.cacheMapMutex.Unlock()

unionfs/unionfs.go

@@ -100,7 +100,6 @@ func NewUnionFs(fileSystems []fuse.FileSystem, options UnionFsOptions) *UnionFs
 	g.branchCache = NewTimedCache(
 		func(n string) (interface{}, bool) { return g.getBranchAttrNoCache(n), true },
 		options.BranchCacheTTL)
-	g.branchCache.RecurringPurge()
 
 	g.hiddenFiles = make(map[string]bool)
 	for _, name := range options.HiddenFiles {