Docker: Ensure that cmd.sh terminates its child processes when the parent script closes photoprism#5172

* Scripts: Ensure that child processes are terminated when parent script closes
* Scripts: Exclude pgrep process id from kill

Author: keif888

scripts/dist/cmd.sh

@@ -1,5 +1,8 @@
 #!/usr/bin/env bash
 
+# clean up child processes via trap
+trap 'ps -p $$ -o pgid= | xargs pgrep -A -g | xargs kill ;exit' EXIT
+
 # regular expressions
 re='^[0-9]+$'