Fix s6-overlay format error (#29)

Add missing shebangs that cause `S6 warning: unable to spawn ./finish: Exec format error` when `ONESHOT=true`. Fixes #28

Also brings the method for killing a container via service exit inline with s6's documented method

Reviewed-on: #29

root/check-one-shot.sh

@@ -4,6 +4,7 @@
 if [ $ONE_SHOT == "true" ]; then
 
     # Cleanly kill container by sending kill signal to supervisor process
-    kill 1
+    echo 0 > /run/s6-linux-init-container-results/exitcode
+    /run/s6/basedir/bin/halt
 
 fi

root/etc/s6-overlay/s6-rc.d/cron/finish

@@ -1 +1,9 @@
-echo "$e" > /run/s6-linux-init-container-results/exitcode
+#!/command/with-contenv bash
+# shellcheck shell=bash
+
+if [ $ONE_SHOT == "false" ]; then
+
+    # Export exit code if not a ONE_SHOT
+    echo "$e" > /run/s6-linux-init-container-results/exitcode
+
+fi

root/etc/s6-overlay/s6-rc.d/logs/finish

@@ -1 +1,9 @@
-echo "$e" > /run/s6-linux-init-container-results/exitcode
+#!/command/with-contenv bash
+# shellcheck shell=bash
+
+if [ $ONE_SHOT == "false" ]; then
+
+    # Export exit code if not a ONE_SHOT
+    echo "$e" > /run/s6-linux-init-container-results/exitcode
+
+fi