Obfuscate execpath from pipeline objects returned to clients

[michelvocks]

Fixes #226

[codecov-io]

Codecov Report

Merging #229 into master will decrease coverage by 0.09%.
The diff coverage is 0%.

@@            Coverage Diff            @@
##           master     #229     +/-   ##
=========================================
- Coverage      62%   61.91%   -0.1%     
=========================================
  Files          49       49             
  Lines        4066     4072      +6     
=========================================
  Hits         2521     2521             
- Misses       1132     1138      +6     
  Partials      413      413

Impacted Files	Coverage Δ
handlers/pipeline.go	53.64% <0%> (-1.42%)	⬇️

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[Skarlso]

Hum, are none of the workers using that for anything?

[michelvocks]

Workers don't use the usual REST API. They use the gRPC interface.