packaging: engine-setup - Add option to generate passwords

Adds a new option to engine-setup: --generate-passwords.
Using this option will allow administrators to run engine-setup in
answer-file mode, so engine will ignore the passwords in the file, and
will generates passwords of it's own, later can be changed via
engine-config/postgres/configuration files.

Change-Id: Ib1e8cfec87e908d8aa5f8d73db91b9c8b02480e1
Signed-off-by: Ofer Schreiber <oschreib@redhat.com>