ipsilon-client-install give password in env. var.
    
    https://fedorahosted.org/ipsilon/ticket/142
    
    If --admin-password is not given, see if the IPSILON_ADMIN_PASSWORD
    environment variable is set, and use it for the admin_password, before
    doing getpass().
    
    Signed-off-by: Rich Megginson <rmeggins@redhat.com>
    Reviewed-by: Patrick Uiterwijk <puiterwijk@redhat.com>