The main `entrypoint.sh` script can now forward SIGUSR1 to `murmurd` multiple times (e.g. multiple certificate updates).

We need to wait each time a signal is captured and forwarded (because wait stops when the child exists OR a signal is received).
And also we need to add a '&' for whatever reason

* Fix function name
* Also, see https://stackoverflow.com/questions/26858344/trap-not-working-in-shell-script