examples/ip_pipeline: add swap action in configuration

examples/ip_pipeline: add swap action in configuration

The network_layers configuration file (config/network_layers.cfg)
demonstrates the various network layer components such as TCP, UDP,
ICMP etc, which can be easily integrated into ip pipeline
infrastructure.

The loopback function (implemented using passthrough pipeline) is
updated to perform swap operation on the IP source and destination
address, and UDP source and destination ports.

Signed-off-by: Jasvinder Singh <jasvinder.singh@intel.com>
Acked-by: Cristian Dumitrescu <cristian.dumitrescu@intel.com>