1. Removed '-P' command line option;
2. Renamed '--passwd' command line option to '--print-password-line'.


mysql-test/t/im_cmd_line.imtest:
  Renamed "--passwd" to "--print-password-line".
server-tools/instance-manager/options.cc:
  1. Removed '-P' option;
  2. Renamed '--passwd' to '--print-password-line'.
server-tools/instance-manager/user_management_commands.cc:
  Renamed class Passwd_cmd to Print_password_line_cmd.
server-tools/instance-manager/user_management_commands.h:
  Renamed class Passwd_cmd to Print_password_line_cmd.