Webserver: handle 500s from director-v2 gracefully

[sanderegg]

What do these changes do?

when some network glitch happens when webserver talks with director-v2 to get the pipeline status a 500 could come back to the frontend. Now this should be catched and an UNKNOWN status is returned.

partially fixes #2155

Related issue/s

How to test

Checklist

[codecov]

Codecov Report

Merging #2202 (683656e) into master (cb75149) will increase coverage by 0.0%.
The diff coverage is 66.6%.

@@          Coverage Diff           @@
##           master   #2202   +/-   ##
======================================
  Coverage    73.0%   73.0%           
======================================
  Files         465     465           
  Lines       17907   17907           
  Branches     1764    1764           
======================================
+ Hits        13086   13088    +2     
+ Misses       4361    4360    -1     
+ Partials      460     459    -1     

Flag	Coverage Δ
integrationtests	65.3% <66.6%> (+<0.1%)	⬆️
unittests	66.4% <66.6%> (ø)

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Impacted Files	Coverage Δ
...erver/src/simcore_service_webserver/director_v2.py	88.1% <66.6%> (+0.8%)	⬆️
...simcore_service_webserver/projects/projects_api.py	86.8% <0.0%> (+0.4%)	⬆️