ClatdController & tests/tun_interface: change from /dev/tun to /dev/net/tun

(this is the upstream default location of the 'tun' special device)

Test: build, atest
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: Ie834a16264dc1188aa9f3fb40cb5e0e5643737cc
2 files changed