We were using sleeps to hope we catch the password prompt. This makes the test
flaky. So I added a help text followed by a `fflush` to make sure we catcht he
right moment, instead of guessing. The `fflush` is also useful for debugging
if a user ever pipes the output to a file it'd get buffered and the user would
wait forever. The same applies for automated systems such as `expect` or
`pexpect` based scripts that enter the password on prompt.
c84473f82c