tagging: fix handling trackers without all fields

[Zariel]

Fix the test for required_seed_days and required_seed_ratio to check if the key is in object otherwise it just throws a KeyError when accessing.

This fixes this error when not specifying either key in the tracker config.

03:00:05 PM ERROR: Error executing command: tagging
Traceback (most recent call last):
  File "/app/qbtools.py", line 135, in main
    mod.__init__(app, logger)
    ~~~~~~~~~~~~^^^^^^^^^^^^^
  File "/app/commands/tagging.py", line 113, in __init__
    tracker["required_seed_ratio"]
    ~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^
KeyError: 'required_seed_ratio'

[buroa]

Thanks @Zariel!

[qlonik]

Hey, sorry, but I think this is a breaking change.

Previously setting seed days or ratio to 0 value would mean it would never expire (because in the check tracker["required_seed_ratio"] the value 0 is falsy). Now the value of 0 will mean the torrents can expire a second after they are added.

[buroa]

@qlonik I saw this immediately after merging and have fixed it: 644cd18