Fix reward flag

[leszko]

What does this pull request do? Explain your changes. (required)
Fix a bug in the reward flag. It stopped working after the refactoring PR #2351. If the flag is set explicitly to true, it does not work. This PR fixes it.

Specific updates (required)

How did you test each of these updates (required)

Tested manually

Does this pull request close any open issues?

N/A

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 #2493 (4604005) into master (5ad8ab5) will decrease coverage by 0.00827%.
The diff coverage is 0.00000%.

@@                 Coverage Diff                 @@
##              master       #2493         +/-   ##
===================================================
- Coverage   54.73000%   54.72173%   -0.00827%     
===================================================
  Files             95          95                 
  Lines          19852       19855          +3     
===================================================
  Hits           10865       10865                 
- Misses          8383        8386          +3     
  Partials         604         604                 

Impacted Files	Coverage Δ
cmd/livepeer/starter/starter.go	2.29665% <0.00000%> (-0.00661%)	⬇️

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