Merge pull request #358 from pantianying/addRlockForDubboInvoker

[fangyincheng]

Fix:deal the panic when invoker destroy

What this PR does:

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[codecov-io]

Codecov Report

Merging #364 into 1.3 will decrease coverage by 0.75%.
The diff coverage is 67.5%.

@@            Coverage Diff             @@
##              1.3     #364      +/-   ##
==========================================
- Coverage   67.85%   67.09%   -0.76%     
==========================================
  Files         118      118              
  Lines        7102     7127      +25     
==========================================
- Hits         4819     4782      -37     
- Misses       1811     1875      +64     
+ Partials      472      470       -2

Impacted Files	Coverage Δ
registry/directory/directory.go	82.8% <66.66%> (-0.88%)	⬇️
protocol/dubbo/dubbo_invoker.go	83.33% <68.42%> (-8.98%)	⬇️
protocol/dubbo/pool.go	58.65% <0%> (-14.91%)	⬇️
protocol/dubbo/listener.go	50.28% <0%> (-10.41%)	⬇️
protocol/dubbo/codec.go	70.27% <0%> (-5.41%)	⬇️
protocol/dubbo/readwriter.go	68.29% <0%> (-2.44%)	⬇️

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