Commands that take passwords should allow input from stdin and not just from controlling terminals

We use installation scripts to configure maxscale, including adding encrypted passwords to /etc/maxscale.cnf using maxpasswd. Requiring a password to be passed to maxpasswd on the command line exposes a security risk if someone is able to ps -ef during the running of this command (however short of a time) and expose the password.

To get around this, we would like to pass the password to maxpasswd and maxadmin via stdin from a python script, which would never allow the password to be exposed. Maxadmin currently allows the password to be passed in stdin, but it will fail if not being run on a terminaal (does tcsetattr). You can attempt to do tcgetattr/tcsetaddr but should not fail if being run on controlling terminal, maybe just print a warning at most.