Start using Hadoop 3 for testing

[nalinigans]

We should probably move to using Hadoop 3 testing TileDB while continuing with Hadoop 2 in GenomicsDB. gatk, for example, is in the process of moving to Hadoop 3 too.

[codecov-commenter]

Codecov Report

Merging #68 into develop will increase coverage by 0.19%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop      #68      +/-   ##
===========================================
+ Coverage    60.99%   61.19%   +0.19%     
===========================================
  Files           50       50              
  Lines        16401    13970    -2431     
===========================================
- Hits         10004     8549    -1455     
+ Misses        6397     5421     -976     

Impacted Files	Coverage Δ
core/src/codec/codec_gzip.cc	86.95% <0.00%> (-4.48%)	⬇️
core/src/fragment/buffer.cc	76.76% <0.00%> (-2.70%)	⬇️
core/src/fragment/read_state.cc	68.31% <0.00%> (-2.09%)	⬇️
core/src/codec/codec_lz4.cc	87.50% <0.00%> (-1.79%)	⬇️
core/include/misc/comparators.h	69.23% <0.00%> (-1.46%)	⬇️
core/src/c_api/tiledb.cc	42.77% <0.00%> (-1.21%)	⬇️
core/src/codec/codec_filter_delta_encode.cc	91.11% <0.00%> (-1.20%)	⬇️
core/src/expressions/expression.cc	87.40% <0.00%> (-0.92%)	⬇️
core/src/codec/codec_filter_bit_shuffle.cc	65.00% <0.00%> (-0.91%)	⬇️
core/include/codec/codec_filter.h	90.90% <0.00%> (-0.76%)	⬇️
... and 26 more

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