SubRange: optimize hashCode

[dhalperi]

No description provided.

[batfish-bot]

This change is 

[progwriter]

Reviewed 1 of 1 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @dhalperi)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.73%. Comparing base (980165c) to head (92a1f73).
Report is 32 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #9271      +/-   ##
==========================================
- Coverage   72.73%   72.73%   -0.01%     
==========================================
  Files        3315     3315              
  Lines      170032   170032              
  Branches    20059    20059              
==========================================
- Hits       123679   123673       -6     
- Misses      37187    37191       +4     
- Partials     9166     9168       +2     

Files with missing lines	Coverage Δ
.../src/main/java/org/batfish/datamodel/SubRange.java	84.31% <100.00%> (ø)

... and 3 files with indirect coverage changes