get_ip_packet: make is_loopback a default parameter

Signed-off-by: Raul Gutierrez S <rgs@twitter.com>
Remove unneeded import in base.sniffer

Signed-off-by: Raul Gutierrez S <rgs@twitter.com>
base.network: small cleanups

Signed-off-by: Raul Gutierrez S <rgs@twitter.com>