Rft: keep the name of protocol registry plugin consistent

[yang20150702]

What this PR does:
keep the name of protocol registry plugin consistent

Which issue(s) this PR fixes:
Fixes #2045

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• All ut passed (run 'go test ./...' in project root)
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[yang20150702]

my last fork only have master branch, I can't checkout 3.0 branch, so I fork again.

[codecov-commenter]

Codecov Report

Merging #2052 (db78644) into 3.0 (33a2901) will decrease coverage by 0.00%.
The diff coverage is 25.00%.

@@            Coverage Diff             @@
##              3.0    #2052      +/-   ##
==========================================
- Coverage   44.66%   44.66%   -0.01%     
==========================================
  Files         283      283              
  Lines       17108    17108              
==========================================
- Hits         7642     7641       -1     
- Misses       8658     8659       +1     
  Partials      808      808              

Impacted Files	Coverage Δ
config/config_loader.go	17.56% <0.00%> (ø)
config/graceful_shutdown.go	3.88% <0.00%> (ø)
config/service_config.go	53.04% <0.00%> (ø)
registry/protocol/protocol.go	72.10% <100.00%> (ø)
metadata/report/delegate/delegate_report.go	26.49% <0.00%> (-8.61%)	⬇️
cluster/cluster/base/cluster_invoker.go	37.77% <0.00%> (+13.33%)	⬆️

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