Tap plugin

This PR adds a plugin to create tap devices.
The plugin adds a tap device to the container.

The plugin has a workaround for a golang netlink library
which does not allow for tap devices with no owner/group
to be created. When no tap owner/group is requested, the
plugin will fall back to using the ip tool for creating
the tap device. A fix to the golang netlink lib is pending.

Signed-off-by: mmirecki <mmirecki@redhat.com>

vendor/github.com/bits-and-blooms/bitset/popcnt_generic.go

@@ -0,0 +1,24 @@
+// +build !go1.9
+// +build !amd64 appengine
+
+package bitset
+
+func popcntSlice(s []uint64) uint64 {
+	return popcntSliceGo(s)
+}
+
+func popcntMaskSlice(s, m []uint64) uint64 {
+	return popcntMaskSliceGo(s, m)
+}
+
+func popcntAndSlice(s, m []uint64) uint64 {
+	return popcntAndSliceGo(s, m)
+}
+
+func popcntOrSlice(s, m []uint64) uint64 {
+	return popcntOrSliceGo(s, m)
+}
+
+func popcntXorSlice(s, m []uint64) uint64 {
+	return popcntXorSliceGo(s, m)
+}