Remove tun/tap from the default device rules

Looking through git blame, this was added by commit 9fac183
aka "Initial commit of runc binary", most probably by mistake.

Obviously, a container should not have access to tun/tap device, unless
it is explicitly specified in configuration.

Now, removing this might create a compatibility issue, but I see no
other choice.

Aside from the obvious misconfiguration, this should also fix the
annoying

> Apr 26 03:46:56 foo.bar systemd[1]: Couldn't stat device /dev/char/10:200: No such file or directory

messages from systemd on every container start, when runc uses systemd
cgroup driver, and the system runs an old (< v240) version of systemd
(the message was presumably eliminated by [1]).

[1] systemd/systemd@d5aecba

Signed-off-by: Kir Kolyshkin <[email protected]>

libcontainer/specconv/spec_linux.go

@@ -302,16 +302,6 @@ var AllowedDevices = []*devices.Device{
 			Allow:       true,
 		},
 	},
-	// tuntap
-	{
-		Rule: devices.Rule{
-			Type:        devices.CharDevice,
-			Major:       10,
-			Minor:       200,
-			Permissions: "rwm",
-			Allow:       true,
-		},
-	},
 }
 
 type CreateOpts struct {