If `make px4_sitl_default` is run, and not `make px4_sitl_default gazebo` then each model instance will throw the following errors:
```
[Err] [Plugin.hh:178] Failed to load plugin libgazebo_gps_plugin.so: libgazebo_gps_plugin.so: cannot open shared object file: No such file or directory
[Err] [Plugin.hh:178] Failed to load plugin libgazebo_multirotor_base_plugin.so: libgazebo_multirotor_base_plugin.so: cannot open shared object file: No such file or directory
[Err] [Plugin.hh:178] Failed to load plugin libgazebo_motor_model.so: libgazebo_motor_model.so: cannot open shared object file: No such file or directory
[Err] [Plugin.hh:178] Failed to load plugin libgazebo_motor_model.so: libgazebo_motor_model.so: cannot open shared object file: No such file or directory
[Err] [Plugin.hh:178] Failed to load plugin libgazebo_motor_model.so: libgazebo_motor_model.so: cannot open shared object file: No such file or directory
[Err] [Plugin.hh:178] Failed to load plugin libgazebo_motor_model.so: libgazebo_motor_model.so: cannot open shared object file: No such file or directory
[Err] [Plugin.hh:178] Failed to load plugin libgazebo_groundtruth_plugin.so: libgazebo_groundtruth_plugin.so: cannot open shared object file: No such file or directory
[Err] [Plugin.hh:178] Failed to load plugin libgazebo_magnetometer_plugin.so: libgazebo_magnetometer_plugin.so: cannot open shared object file: No such file or directory
[Err] [Plugin.hh:178] Failed to load plugin libgazebo_barometer_plugin.so: libgazebo_barometer_plugin.so: cannot open shared object file: No such file or directory
[Err] [Plugin.hh:178] Failed to load plugin libgazebo_mavlink_interface.so: libgazebo_mavlink_interface.so: cannot open shared object file: No such file or directory
[Err] [Plugin.hh:178] Failed to load plugin libgazebo_imu_plugin.so: libgazebo_imu_plugin.so: cannot open shared object file: No such file or directory
```
- make sure to kill all px4 instances and gazebo client when exiting
- add arguments to specify number of vehicles and vehicle model
- exit for now if vehicle model is not iris, since needs changes in
sitl_gazebo submodule
Signed-off-by: RomanBapst <bapstroman@gmail.com>
JaeyoungLim
Beat Küng
SungTae Moon
Jan-Hendrik Ewers
JaeyoungLim
RomanBapst