bots: ignore NULL bytes in all csv parsers

[ghost]

fixes #967

[codecov-io]

Codecov Report

Merging #1114 into maintenance will increase coverage by 0.01%.
The diff coverage is 100%.

@@               Coverage Diff               @@
##           maintenance    #1114      +/-   ##
===============================================
+ Coverage        75.19%   75.21%   +0.01%     
===============================================
  Files              216      216              
  Lines             9197     9203       +6     
  Branches          1245     1245              
===============================================
+ Hits              6916     6922       +6     
  Misses            1996     1996              
  Partials           285      285

Impacted Files	Coverage Δ
intelmq/bots/parsers/shadowserver/parser.py	83.96% <ø> (ø)	⬆️
intelmq/bots/parsers/turris/parser.py	92% <100%> (+0.33%)	⬆️
intelmq/bots/parsers/generic/parser_csv.py	88.88% <100%> (+0.17%)	⬆️
intelmq/lib/bot.py	63.97% <100%> (+0.16%)	⬆️
intelmq/bots/parsers/abusech/parser_ransomware.py	97.56% <100%> (+0.06%)	⬆️
intelmq/bots/parsers/phishtank/parser.py	48.14% <100%> (+1.99%)	⬆️