Make all ospd-openvas config files more consistent:

[cfi-gb]

• Don't use a DEBUG level in the example config file
• Add various default and more sane config parameters
  to the environment file
• Pass the arguments of the environment file to the systemd
  service

This has various reasons:

1. We shouldn't tell the user to use /var/run/ospd/ospd.sock and/or /var/run/ospd.sock because there might be multiple OSPD scanners in the future
2. Similar to 1. for /var/run/ospd.pid
3. All other GVM components (gvmd, greenbone-nvt-sync) are expecting the feed-update.lock in <install-prefix>/var/run with GVM-20.08 (see Simplify sync lockfile handling gvmd#1059 and Use flock to lock the feed lock file. openvas-scanner#507) but the current default is /var/run/ospd

[codecov]

Codecov Report

Merging #311 into ospd-openvas-20.08 will decrease coverage by 0.82%.
The diff coverage is 51.02%.

@@                  Coverage Diff                   @@
##           ospd-openvas-20.08     #311      +/-   ##
======================================================
- Coverage               82.71%   81.89%   -0.83%     
======================================================
  Files                       9        9              
  Lines                    1481     1513      +32     
======================================================
+ Hits                     1225     1239      +14     
- Misses                    256      274      +18     

Impacted Files	Coverage Δ
ospd_openvas/daemon.py	62.12% <35.00%> (-0.78%)	⬇️
ospd_openvas/preferencehandler.py	87.15% <50.00%> (+0.04%)	⬆️
ospd_openvas/db.py	96.24% <55.00%> (-3.36%)	⬇️
ospd_openvas/lock.py	85.96% <100.00%> (+0.25%)	⬆️
ospd_openvas/openvas.py	100.00% <100.00%> (ø)

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[bjoernricks]

I am not sure if we still should ship example like files or if we just should use concrete paths. Personally I am in favor of concrete paths.

[cfi-gb]

The main problem i'm seeing is that we currently can't use something like cmake to configure / set the path during setup time like it is done when compiling other components.