Update truck-quadplane launch script

[srmainwaring]

• Remove unused and redundant parameters and variables
• AUTO_OPTIONS only applies to copter (used in the copter follow examples, but not relevant for plane and rover)
• Remove --slave and --sysid from command line (SYSID_THISMAV is already set in extra params)
• Remove IGN_* env vars as Ignition is not launched from this script

@tridge I expect you may want to rework both this and the change to the MAVProxy launch in https://github.com/ArduPilot/SITL_Models/pull/70 to use mcast in which case I'll close them unmerged.

[tridge]

conversion to mcast can be done separately