zdtm: Drop tun test from auto-list

There's some strange setup on Jenkins boxes, so that /dev/net/tun
is inaccessible. Need to check this after holidays :(
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

test/zdtm.sh

@@ -116,7 +116,6 @@ static/shm
 static/msgque
 static/sem
 transition/ipc
-ns/static/tun
 "
 
 TEST_CR_KERNEL="