Add lock-file-dir configuration option.

[jjnicola]

By default the directory is /var/run/ospd. In this directory can be placed lock files in case of need.
E.g.: during feed update to block other processes.

[codecov]

Codecov Report

Merging #217 into ospd-2.0 will increase coverage by 0.03%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           ospd-2.0    #217      +/-   ##
===========================================
+ Coverage     68.07%   68.1%   +0.03%     
===========================================
  Files            12      12              
  Lines          1873    1875       +2     
===========================================
+ Hits           1275    1277       +2     
  Misses          598     598

Impacted Files	Coverage Δ
ospd/parser.py	87.5% <100%> (+0.32%)	⬆️

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