FIX: pricePerBroadcaster JSON file line breaks parsing bug

[thomshutt]

!! Based on #2913 from @rickstaa !!

What does this pull request do? Explain your changes. (required)
The current go-livepeer livepeer binary does not correctly parse pricePerBroadcaster files if they contain line breaks.

This pull request ensures that the pricePerBroadcaster flag also works with JSON files that contain line breaks as is often done to improve readability.

As far as I could tell, the previous iteration was done as a way to make sure single line + newline files that contained e.g a password parsed correctly and didn't bring in the newline.

Specific updates (required)

• The common.ReadFromFile was changed so JSON files with line breaks and JSON strings are parsed correctly.

How did you test each of these updates (required)

• Ran unit tests, tried parsing multiline JSON files.

Does this pull request close any open issues?
Fixes #2912

Checklist:

• Read the contribution guide
• make runs successfully
• All tests in ./test.sh pass
• README and other documentation updated
• Pending changelog updated

[codecov]

Codecov Report

Merging #2914 (ae3b83b) into master (5b69cd6) will decrease coverage by 0.01563%.
The diff coverage is 100.00000%.

Additional details and impacted files

@@                 Coverage Diff                 @@
##              master       #2914         +/-   ##
===================================================
- Coverage   56.54162%   56.52599%   -0.01563%     
===================================================
  Files             89          89                 
  Lines          19460       19453          -7     
===================================================
- Hits           11003       10996          -7     
  Misses          7849        7849                 
  Partials         608         608                 

Files	Coverage Δ
common/readfromfile.go	85.00000% <100.00000%> (-3.88889%)	⬇️

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Files	Coverage Δ
common/readfromfile.go	85.00000% <100.00000%> (-3.88889%)	⬇️

[rickstaa]

Thanks for adding me as a co-author ❤️‍🔥.