Fix overlapping theta boundary in spherical KDE reconstructions

[clevelam]

Background

• Add some extra ensures to protect off-processor data fetching.

Purpose of Pull Request

• Fix some sign mistakes in the overlapping theta mapping for quick_index
• Fixes re-git issue #1358

Description of changes

• Fix theta=0,2pi overlap boundaries

Status

• Reference:
  • Pre-Merge Code Review
  • CDash Status
• Checks
  • Travis/Appveyor CI checks pass
  • Code coverage does not decrease
  • Valgrind test passes
  • Toss3 checks pass
  • Trinitite checks pass
  • Code reviewed/approved, sufficient DbC checks, testing, documentation

[codecov]

Codecov Report

Merging #1125 (09a0937) into develop (347d3d1) will not change coverage.
The diff coverage is 100.0%.

@@           Coverage Diff           @@
##           develop   #1125   +/-   ##
=======================================
  Coverage     89.0%   89.0%           
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  Files          374     374           
  Lines        19261   19261           
=======================================
  Hits         17157   17157           
  Misses        2104    2104