Switch to github.com/golang/dep for vendoring

Signed-off-by: Mrunal Patel <mrunalp@gmail.com>

vendor/github.com/Microsoft/hcsshim/preparelayer.go

@@ -0,0 +1,46 @@
+package hcsshim
+
+import (
+	"sync"
+
+	"github.com/Sirupsen/logrus"
+)
+
+var prepareLayerLock sync.Mutex
+
+// PrepareLayer finds a mounted read-write layer matching layerId and enables the
+// the filesystem filter for use on that layer.  This requires the paths to all
+// parent layers, and is necessary in order to view or interact with the layer
+// as an actual filesystem (reading and writing files, creating directories, etc).
+// Disabling the filter must be done via UnprepareLayer.
+func PrepareLayer(info DriverInfo, layerId string, parentLayerPaths []string) error {
+	title := "hcsshim::PrepareLayer "
+	logrus.Debugf(title+"flavour %d layerId %s", info.Flavour, layerId)
+
+	// Generate layer descriptors
+	layers, err := layerPathsToDescriptors(parentLayerPaths)
+	if err != nil {
+		return err
+	}
+
+	// Convert info to API calling convention
+	infop, err := convertDriverInfo(info)
+	if err != nil {
+		logrus.Error(err)
+		return err
+	}
+
+	// This lock is a temporary workaround for a Windows bug. Only allowing one
+	// call to prepareLayer at a time vastly reduces the chance of a timeout.
+	prepareLayerLock.Lock()
+	defer prepareLayerLock.Unlock()
+	err = prepareLayer(&infop, layerId, layers)
+	if err != nil {
+		err = makeErrorf(err, title, "layerId=%s flavour=%d", layerId, info.Flavour)
+		logrus.Error(err)
+		return err
+	}
+
+	logrus.Debugf(title+"succeeded flavour=%d layerId=%s", info.Flavour, layerId)
+	return nil
+}