iptrunk_checks

Optical PRE and POST checks:
- optical values are extracted per AE member, per lane and are written
into local file of LSO container;
- in the POST check the diff is produced on the optical values of the
remaining side;

Changes to the ping test:
- Separate "rapid" ping and "mtu" ping with the respective "ping_size"
and "ping_count" values (currently in the role's vars).