selftests/net: add nettest to .gitignore

nettest is missing from gitignore.

Fixes: acda655fefae ("selftests: Add nettest")
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
1 file changed