project: use vndr for vendoring

Signed-off-by: Alexander Morozov <lk4d4@docker.com>

vendor/github.com/pivotal-golang/clock/clock.go

@@ -0,0 +1,42 @@
+package clock
+
+import "time"
+
+type Clock interface {
+	Now() time.Time
+	Sleep(d time.Duration)
+	Since(t time.Time) time.Duration
+
+	NewTimer(d time.Duration) Timer
+	NewTicker(d time.Duration) Ticker
+}
+
+type realClock struct{}
+
+func NewClock() Clock {
+	return &realClock{}
+}
+
+func (clock *realClock) Now() time.Time {
+	return time.Now()
+}
+
+func (clock *realClock) Since(t time.Time) time.Duration {
+	return time.Now().Sub(t)
+}
+
+func (clock *realClock) Sleep(d time.Duration) {
+	<-clock.NewTimer(d).C()
+}
+
+func (clock *realClock) NewTimer(d time.Duration) Timer {
+	return &realTimer{
+		t: time.NewTimer(d),
+	}
+}
+
+func (clock *realClock) NewTicker(d time.Duration) Ticker {
+	return &realTicker{
+		t: time.NewTicker(d),
+	}
+}