Bug 17746: (QA follow-up) Make set_password.pl generate a password if required

Bug 17746: (QA follow-up) Make set_password.pl generate a password if required

This patch makes the set_password.pl script generate the password if it
is not passed as an argument.

It also changes the behaviour of set_password.pl: it will now print the
userid and password (generated or not) to mimick the behaviour from
koha-reset-passwd.

The koha-reset-passwd gets simplified as it doesn't generate the random
password anymore, it passes the responsability to set_password.pl

To test:
- Follow the steps from the original platch
- Verify all behaves as expected

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Liz Rea <wizzyrea@gmail.com>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>