Add exit-service

[siegfriedweber]

• exit-service added

$ cat exit-service-1.0.0/start.sh
#!/bin/sh

exit $EXIT_CODE

• Services sorted alphabetically in the READMEs.
• Long lines reformatted.

The exit-service is used to test stackabletech/agent#117.

[soenkeliebau]

LGTM overall, just one question..

It seems to me that the implementation of returning 0 when EXIT_CODE is not set relies on the behavior of exit when it receives no parameter?
I googled briefly and found this sentence:

If N is omitted, the exit status is that of the last command executed.

I'm probably way of the reservation here and you considered this, so by all means feel free to merge as is, just a thought that occurred to me!

[siegfriedweber]

It seems to me that the implementation of returning 0 when EXIT_CODE is not set relies on the behavior of exit when it receives no parameter?
I googled briefly and found this sentence:

If N is omitted, the exit status is that of the last command executed.

The initial error status is 0. If there is no "last command" then this initial error status is returned. This is concise but I must admit that extending the code is hard because the command before exit must never return anything than 0. So I changed the code:

#!/bin/sh

exit ${EXIT_CODE:-0}

[soenkeliebau]

LGTM