Forward upstream exit code on `cloudron exec`

[nebulon]

One takeaway from the meetup yesterday, if cloudron exec runs a remote command and exits, it will not forward the remote command's exit code, but basically always returns 0. This makes it harder to be used in piplines or shell scripts.

We should be able to get the remote exit code and then set that one as the cloudron exit code.

[girish]

We need to add a separate API to get exit status of exec container.

[girish]

This is implemented in 7.2.1.

~$ cloudron exec --app orkut -- bash -c 'exit 42'
~$ echo $?
42