Init celery application in app once + run call to blocking call in executor

[sanderegg]

What do these changes do?

• the celery application is initialized once at the beginning (will later need to check what happens if Rabbit/Redis are restarted) (but if scheduler is changed, then we might ditch this)
• run call to celery inspect in executor

Related issue/s

How to test

Checklist

[codecov]

Codecov Report

Merging #2372 (c9449d0) into master (dc4c691) will decrease coverage by 8.7%.
The diff coverage is 72.4%.

❗ Current head c9449d0 differs from pull request most recent head 0fbbb06. Consider uploading reports for the commit 0fbbb06 to get more accurate results

@@           Coverage Diff            @@
##           master   #2372     +/-   ##
========================================
- Coverage    74.3%   65.6%   -8.8%     
========================================
  Files         395     514    +119     
  Lines       16941   20019   +3078     
  Branches     1781    1967    +186     
========================================
+ Hits        12599   13146    +547     
- Misses       3870    6456   +2586     
+ Partials      472     417     -55     

Flag	Coverage Δ
integrationtests	?
unittests	65.6% <72.4%> (-4.4%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...src/simcore_service_webserver/computation_utils.py	100.0% <ø> (ø)
...src/simcore_service_webserver/activity/handlers.py	27.1% <33.3%> (-62.9%)	⬇️
...simcore_service_webserver/activity/module_setup.py	52.6% <50.0%> (-47.4%)	⬇️
...imcore_service_webserver/activity/celery_client.py	75.0% <75.0%> (ø)
...r/src/simcore_service_webserver/activity/config.py	85.7% <100.0%> (-14.3%)	⬇️
...webserver/computation_comp_tasks_listening_task.py	62.0% <100.0%> (-22.0%)	⬇️
...ackages/simcore-sdk/src/simcore_sdk/models/base.py	0.0% <0.0%> (-100.0%)	⬇️
...ges/simcore-sdk/src/simcore_sdk/models/__init__.py	0.0% <0.0%> (-100.0%)	⬇️
...erver/src/simcore_service_webserver/rest_models.py	0.0% <0.0%> (-91.2%)	⬇️
...es/web/server/src/simcore_service_webserver/cli.py	0.0% <0.0%> (-73.9%)	⬇️
... and 212 more

[pcrespov]

flash SAN ⚡ !

[GitHK]

👍