Pass SIGTERM to child process and wait

[maggie44]

When stopping the secure store container the sigterm/sigkill etc will be passed to the secure store process and will terminate without waiting for the child process (the users app) to exit gracefully.

secure-store/cmd/secure-store/run/run.go

Line 27 in 3a51a23

err := cmd.Run()

Signal handlers should be added to pass the sigterm commands to the child process to allow graceful exit and to avoid data loss in the users app.