Check if the scan was stopped before launching OpenVAS.

[jjnicola]

What:
Check if the scan was stopped before launching OpenVAS.

Why:
If the scan was stopped during the preferences handling before spawining the OpenVAS process,
the process was spawned but still marked as stopped.
Now the scan is indeed stopped and the new process is not being spawned.

How:
The issue is that ospd-openvas set the task as running, while it is still preparing the scan preferences to be sent to the scanner. In other words, Openvas has not been started when ospd-openvas received the stop command.

With a small scan config, this problem is probably harder to reproduce, since ospd-openvas prepares the preferences and starts Openvas faster

If you see in the logs, you can see that Openvas is started after the stop cmd is received. If you wait until Openvas is indeed started, the scan is stopped as expected.

To reproduce the issue and check the fix:

1. Start a task with a "Full and fast" scan against a /24 network
2. Once the task is displayed as "Running", stop it by clicking on the "Stop" icon.

Checklist:

• Tests N/A
• [x ] CHANGELOG Entry

[codecov]

Codecov Report

Merging #332 into ospd-openvas-20.08 will decrease coverage by 0.81%.
The diff coverage is 54.54%.

@@                  Coverage Diff                   @@
##           ospd-openvas-20.08     #332      +/-   ##
======================================================
- Coverage               82.71%   81.90%   -0.82%     
======================================================
  Files                       9        9              
  Lines                    1481     1514      +33     
======================================================
+ Hits                     1225     1240      +15     
- Misses                    256      274      +18     

Impacted Files	Coverage Δ
ospd_openvas/daemon.py	62.12% <33.33%> (-0.78%)	⬇️
ospd_openvas/db.py	96.24% <57.14%> (-3.36%)	⬇️
ospd_openvas/preferencehandler.py	87.15% <66.66%> (+0.04%)	⬆️
ospd_openvas/__version__.py	100.00% <100.00%> (ø)
ospd_openvas/lock.py	85.96% <100.00%> (+0.25%)	⬆️
ospd_openvas/nvticache.py	98.49% <100.00%> (+0.01%)	⬆️
ospd_openvas/openvas.py	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 63e4db4...5509315. Read the comment docs.