Fix race condition when fetching results in SQL Lab

[betodealmeida]

SUMMARY

There's a race condition causing results to not be returned by SQL Lab. An eager commit saves the query object with its status set to SUCCESS, but only later it updates the resultsKey:

    query.status = QueryStatus.SUCCESS
    session.commit()  # HERE
    ...
    if store_results:
        key = str(uuid.uuid4())
        ...
        query.results_key = key
    session.commit()

I simply deleted the first commit, and now the results are always returned.

I also fixed the execute_sql_statement function. It was taking an argument return_results which was not being used anywhere.

TEST PLAN

I ran queries in SQL Lab, and they returned 100% of the time. Before, occasionally they wouldn't return anything because state was set to SUCCESS, but the query object had no resultsKeys attribute.

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
[x] Fixes bug
[ ] Refactors code
[ ] Adds test(s)

REVIEWERS

@xtinec @DiggidyDave @khtruong @enricoberti

[xtinec]

yes!!!!!

[codecov-io]

Codecov Report

Merging #7198 into lyftga will decrease coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           lyftga    #7198      +/-   ##
==========================================
- Coverage   64.52%   64.51%   -0.01%     
==========================================
  Files         424      424              
  Lines       20684    20682       -2     
  Branches     2268     2268              
==========================================
- Hits        13346    13344       -2     
  Misses       7216     7216              
  Partials      122      122

Impacted Files	Coverage Δ
superset/sql_lab.py	76.37% <100%> (-0.26%)	⬇️
superset/views/core.py	75% <100%> (ø)	⬆️

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