Bug 22253: Check we actually need to update the password

Bug 22253: Check we actually need to update the password

This patch makes memberentry.pl check if password needs to be updated
before attempting to call set_password. Above this there's a check that
won't raise any errors if no password is passed, or the default string (****) is received.

So we could reach that line of code with no password, but the code
wouldn't check that.

To test:
- In master, edit any patron without changing the password
=> FAIL: It raises an exception
- Apply this patch
- Edit the patron withtout changing the password
=> SUCCESS: Edit successful
- Edit the patron, changing the password
- Try to login with the new password
=> SUCCESS: The password got changed correctly
- Sigh off :-D

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>