IOTEX-1025 update consensus messages

[CoderZhi]

To eliminate confusion.

[codecov]

Codecov Report

Merging #1038 into master will decrease coverage by 0.01%.
The diff coverage is 50%.

@@            Coverage Diff             @@
##           master    #1038      +/-   ##
==========================================
- Coverage   54.29%   54.28%   -0.02%     
==========================================
  Files         159      159              
  Lines       13631    13631              
==========================================
- Hits         7401     7399       -2     
- Misses       5244     5245       +1     
- Partials      986      987       +1

Impacted Files	Coverage Δ
consensus/scheme/rolldpos/rolldposctx.go	61.98% <50%> (ø)	⬆️
db/trie/extensionnode.go	57.62% <0%> (-1.7%)	⬇️

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