test: speedup celery tests

[kstrz]

SUMMARY

Speedup async celery tests by querying db in 0.5 s intervals instead of waiting 6s.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TEST PLAN

ADDITIONAL INFORMATION

• Has associated issue:
• Changes UI
• Requires DB Migration.
• Confirm DB Migration upgrade and downgrade tested.
• Introduces new feature or API
• Removes existing feature or API

[kstrz]

Hey! Could you look at it? @willbarrett @dpgaspar

[codecov-io]

Codecov Report

Merging #12885 (f350b57) into master (2adfb85) will decrease coverage by 1.51%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #12885      +/-   ##
==========================================
- Coverage   64.89%   63.38%   -1.52%     
==========================================
  Files        1024      489     -535     
  Lines       50168    30197   -19971     
  Branches     5148        0    -5148     
==========================================
- Hits        32557    19139   -13418     
+ Misses      17433    11058    -6375     
+ Partials      178        0     -178     

Flag	Coverage Δ
cypress	?
javascript	?
python	63.38% <ø> (-0.71%)	⬇️

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

Impacted Files	Coverage Δ
superset/sql_validators/postgres.py	50.00% <0.00%> (-50.00%)	⬇️
superset/views/database/views.py	62.50% <0.00%> (-25.07%)	⬇️
superset/databases/commands/create.py	83.67% <0.00%> (-8.17%)	⬇️
superset/databases/commands/update.py	85.71% <0.00%> (-8.17%)	⬇️
superset/sql_validators/base.py	93.33% <0.00%> (-6.67%)	⬇️
superset/db_engine_specs/base.py	79.59% <0.00%> (-6.38%)	⬇️
superset/db_engine_specs/presto.py	82.25% <0.00%> (-6.28%)	⬇️
superset/db_engine_specs/sqlite.py	90.62% <0.00%> (-6.25%)	⬇️
superset/views/database/forms.py	83.33% <0.00%> (-5.56%)	⬇️
superset/databases/commands/test_connection.py	84.78% <0.00%> (-4.35%)	⬇️
... and 547 more

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[dpgaspar]

Nice catch! the wait loop could be method so you don't repeat yourself

[kstrz]

Hey! Could you look at it? @willbarrett @dpgaspar