Allow abilitiy to boot controller with non-default admin credentials

  - Default admin password can be overridden using the reset
    mechanism. NETWORK_ADMIN_PASSWORD_RECOVERY can optionally
    contain the password to be reset to.
  - Provide optional configuration to disallow factory default
    password. (-Dusermanager.disable-default-admin-password=true)
  - Convert ATN & ATZ security sensitive messages to 'trace' level
    instead of 'info' level

Change-Id: I7dcaf15e8d562f61a3a4636a8abc244b0d6365ae
Signed-off-by: Prasanth Pallamreddy <ppallamr@cisco.com>