Write spill instead of partition data file

[jealous]

For the bypass merge sort shuffle code path, use the make spill file API instead of the make shuffle data file API provided by the storage plugin to avoid the file already exists error.

[codecov[bot]]

Codecov Report

Merging #28 into master will decrease coverage by 0.03%. The diff coverage is 50%.

@@             Coverage Diff              @@
##             master      #28      +/-   ##
============================================
- Coverage     75.78%   75.74%   -0.04%     
- Complexity      435      437       +2     
============================================
  Files            30       30              
  Lines          2044     2045       +1     
  Branches        332      332              
============================================
  Hits           1549     1549              
  Misses          275      275              
- Partials        220      221       +1

Impacted Files	Coverage Δ	Complexity Δ
...k/shuffle/SplashBypassMergeSortShuffleWriter.scala	78.31% <50%> (-0.96%)	22 <2> (+2)

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 6145ded...e828a30. Read the comment docs.

[jealous]

Work on another solution.