Sometimes "arming - takeoff" sequence fails

[jnippula]

When calling ros2 service call for arming and immediately after that ros2 service call for takeoff, the drone sometimes just rotates the rotors for a while and disarms until the takeoff command is confirmed and executed.
Somehow the service to come available is taking too long.

[jnippula]

This is still an issue, but it occurs a bit more sheldom due to increased PX4 disarm timeout.

[stibipet]

Probably related to the DDS discovery server in Foxy. This may improve with future system updates or upgrading to ros2 Galactic.