fix: Dashboard export loading indicator

[michael-s-molina]

SUMMARY

When exporting a dashboard, if the feature flag VERSIONED_EXPORT was set to false, the loading indicator would persist even after the download completes. This PR makes sure the export token used to control the status is set independently of the feature flag.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

Screen.Recording.2021-12-01.at.11.39.55.AM.mov

Screen.Recording.2021-12-01.at.11.42.04.AM.mov

TESTING INSTRUCTIONS

Check the videos for instructions.

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[betodealmeida]

Oh, good catch!

[codecov]

Codecov Report

Merging #17613 (4c35a06) into master (d7e3a60) will decrease coverage by 0.10%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master   #17613      +/-   ##
==========================================
- Coverage   68.59%   68.48%   -0.11%     
==========================================
  Files        1588     1601      +13     
  Lines       64948    65260     +312     
  Branches     6963     6963              
==========================================
+ Hits        44548    44693     +145     
- Misses      18510    18677     +167     
  Partials     1890     1890              

Flag	Coverage Δ
hive	81.38% <66.66%> (-0.23%)	⬇️
mysql	81.80% <66.66%> (-0.23%)	⬇️
postgres	81.81% <66.66%> (-0.23%)	⬇️
presto	?
python	82.15% <66.66%> (-0.38%)	⬇️
sqlite	81.49% <66.66%> (-0.23%)	⬇️

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

Impacted Files	Coverage Δ
superset/dashboards/api.py	91.86% <66.66%> (-0.29%)	⬇️
superset/db_engine_specs/presto.py	84.34% <0.00%> (-6.06%)	⬇️
superset/utils/cache_manager.py	96.15% <0.00%> (-3.85%)	⬇️
superset/connectors/sqla/models.py	87.07% <0.00%> (-1.35%)	⬇️
superset/models/core.py	89.26% <0.00%> (-0.74%)	⬇️
superset/key_value/commands/update.py	57.69% <0.00%> (ø)
superset/key_value/commands/delete.py	60.00% <0.00%> (ø)
...uperset/dashboards/filter_state/commands/delete.py	63.63% <0.00%> (ø)
superset/key_value/commands/get.py	57.14% <0.00%> (ø)
...uperset/dashboards/filter_state/commands/update.py	63.63% <0.00%> (ø)
... and 10 more

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