move to exec

this change uses the s6 death tally logic to check if it's the first
start of the service, if it's not it will delay the start of airspy_adsb

in the usual case of a normal container startup, airspy_adsb is
instantly started up with exec which frees some memory used by bash

rootfs/etc/s6-overlay/scripts/airspy_adsb

@@ -2,7 +2,6 @@
 #shellcheck shell=bash disable=SC1091
 
 source /scripts/common
-trap 'pkill -P $$' SIGTERM SIGINT SIGHUP SIGQUIT
 
 s6wrap=(s6wrap --quiet --prepend="$(basename "$0")" --timestamps --args)
 
@@ -167,11 +166,11 @@ fi
 "${s6wrap[@]}" echo "Running: ${AIRSPY_ADSB_BIN} ${AIRSPY_ADSB_CMD[*]}"
 
 # Slow down restarts
-sleep 10 &
+# wait 30 seconds if this is not the first startup (this should only happen on crashes or a bad command line, thus this can be a long timeout)
+if [[ $(s6-svdt /run/service/airspy_adsb | wc -l) != 0 ]]; then
+    "${s6wrap[@]}" echo "delaying restart by 30 seconds"
+    sleep 30
+fi
 
 #shellcheck disable=SC2016
-"${s6wrap[@]}" "${AIRSPY_ADSB_BIN}" "${AIRSPY_ADSB_CMD[@]}" &
-
-# trap will only work properly while the shell is running / waiting, not while another program is being foreground executed
-# the first wait exits due to the signal which is trapped, the 2nd wait actually waits for collectd to exit
-wait || wait || true
+exec "${s6wrap[@]}" "${AIRSPY_ADSB_BIN}" "${AIRSPY_ADSB_CMD[@]}"