Some parameters with default values throw AttributeError when not set

[gethvi]

If I omit some parameters from the configuration (that are supposed to have default values, e.g. mail_ssl (True) for intelmq.bots.collectors.mail and delimiter (,) for intelmq.bots.parsers.generic.csv), I get an AttributeError:

Bot has found a problem.
Traceback (most recent call last):
  File "/usr/local/lib/python3.5/dist-packages/intelmq/lib/bot.py", line 269, in start
    self.process()
  File "/usr/local/lib/python3.5/dist-packages/intelmq/bots/collectors/mail/lib.py", line 40, in process
    mailbox = self.connect_mailbox()
  File "/usr/local/lib/python3.5/dist-packages/intelmq/bots/collectors/mail/lib.py", line 33, in connect_mailbox
    self.parameters.mail_ssl,
AttributeError: 'Parameters' object has no attribute 'mail_ssl'

This is also reason why in #1571 I explicitly mentioned missing delimiter.

I only came across mail_ssl and delimiter lately when I wanted to count on their default value. There might be more parameters with this behavior.

[ghost]

I think this is a duplicate of #757

[ghost]

Duplicate of #757