If user exists, don't ask for a new password

[alexghergh]

Right now, if a user exists AND IS THE USER RUNNING THE SCRIPT, then the password won't change.
Otherwise, if a different user is running the script, BUT THE USER IN THE HOSTS_VARS FILE STILL EXISTS, then the password will be modified for that user.

Change the script to NOT ask for a password if the user is already present on the system, regardless of it being or not the user running the script.