init.d-posix: exit on error

This fixes a case where the px4 startup is not stopped when the
px4 process is killled using -SIGKILL against the px4 deamon.
In that case, the currently executing command/client is killed
and properly shutting down with result -1, however, the next command
is started anyway.

This means that the next time we try to run the simulation we get a
"PX4 daemon already running for instance 0" error and PX4 doesn't start
properly.

By adding exit on error, we properly exit in the case where the startup
script gets stopped/killed.

ROMFS/px4fmu_common/init.d-posix/rcS

@@ -1,5 +1,7 @@
 #!/bin/sh
 
+set -e
+
 # PX4 commands need the 'px4-' prefix in bash.
 # (px4-alias.sh is expected to be in the PATH)
 # shellcheck disable=SC1091