Fix:load protocol

[hxmhlt]

What this PR does:
Fix load protocol

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:
Yes.
User's server.yaml which defined as

services:
  "UserProvider":
       protocol : "myDubbo"
  xxxx

protocol value should match key in protocols map defined as follow.

protocols:
    "myDubbo":
      name: "dubbo"
      ip : "127.0.0.1"
      port : 20000

[codecov-io]

Codecov Report

Merging #218 into develop will increase coverage by 0.04%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           develop     #218      +/-   ##
===========================================
+ Coverage    66.03%   66.07%   +0.04%     
===========================================
  Files           96       96              
  Lines         6459     6459              
===========================================
+ Hits          4265     4268       +3     
+ Misses        1747     1745       -2     
+ Partials       447      446       -1

Impacted Files	Coverage Δ
config/protocol_config.go	100% <100%> (ø)	⬆️
protocol/jsonrpc/server.go	61.3% <0%> (+1.5%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 519aee1...15d792c. Read the comment docs.