Don't separately allocate sync.{Mutex,Once} if not necessary

Separate allocation of synchronization devices suggests they're shared
between objects, but they're not.

internal/fs/fs_local_vss.go

@@ -21,7 +21,7 @@ type LocalVss struct {
 	FS
 	snapshots       map[string]VssSnapshot
 	failedSnapshots map[string]struct{}
-	mutex           *sync.RWMutex
+	mutex           sync.RWMutex
 	msgError        ErrorHandler
 	msgMessage      MessageHandler
 }
@@ -36,7 +36,6 @@ func NewLocalVss(msgError ErrorHandler, msgMessage MessageHandler) *LocalVss {
 		FS:              Local{},
 		snapshots:       make(map[string]VssSnapshot),
 		failedSnapshots: make(map[string]struct{}),
-		mutex:           &sync.RWMutex{},
 		msgError:        msgError,
 		msgMessage:      msgMessage,
 	}

internal/restic/progress.go

@@ -40,7 +40,7 @@ type Progress struct {
 	start      time.Time
 	c          *time.Ticker
 	cancel     chan struct{}
-	o          *sync.Once
+	once       sync.Once
 	d          time.Duration
 	lastUpdate time.Time
 
@@ -79,7 +79,6 @@ func (p *Progress) Start() {
 		return
 	}
 
-	p.o = &sync.Once{}
 	p.cancel = make(chan struct{})
 	p.running = true
 	p.Reset()
@@ -187,7 +186,7 @@ func (p *Progress) Done() {
 	}
 
 	p.running = false
-	p.o.Do(func() {
+	p.once.Do(func() {
 		close(p.cancel)
 	})