Fix unknown command issue in sentinel-transport-netty-http module

[cdfive]

Describe what this PR does / why we need it

If a command whose mapping path and command name has more than one "/",
the CommandHandler can't be found in sentinel-transport-netty-http,
such as:
/cluster/server/flowRules
FetchClusterFlowRulesCommandHandler
will case:
Unknown command "cluster"

Does this pull request fix one issue?

Fixes #810

Describe how you did it

Modify the String parseTarget(String uri) method in HttpServerHandler class.
Don't use uri.split("/") to parse, but use indexOf("/") instead, to remove the
/ in uri, just like the parseRequest method of HttpEventTask class in sentinel-transport-simple-http module.

Describe how to verify it

Add 2 test cases in HttpServerHandlerTest class:
testFetchClusterFlowRulesCommandEmptyRule
testFetchClusterFlowRulesCommandSomeFlowRules
In order to test, sentinel-cluster-server-default dependency is added with test scope.

Run demo in sentinel-demo-cluster-server-alone module,
change the sentinel-transport-simple-http to sentinel-transport-netty-http,
start the ClusterServerDemo and visit http://localhost:8719/cluster/server/flowRules

Special notes for reviews

The previous test case which marked FIXME in HttpServerHandlerTest class has been fixed, I found a way that we can call embeddedChannel.readOutbound() looply to get the whole result.

Some comments in test class have been improved, such as upper case the first letter.

In pom.xml of parent module, sentinel-transport-netty-http is added in <dependencyManagement> , so that we needn't add version number when use it.

[codecov-io]

Codecov Report

Merging #817 into master will increase coverage by 0.05%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #817      +/-   ##
============================================
+ Coverage     41.71%   41.77%   +0.05%     
- Complexity     1376     1378       +2     
============================================
  Files           304      304              
  Lines          8764     8764              
  Branches       1182     1182              
============================================
+ Hits           3656     3661       +5     
+ Misses         4662     4658       -4     
+ Partials        446      445       -1

Impacted Files	Coverage Δ	Complexity Δ
...a/csp/sentinel/slots/statistic/base/LeapArray.java	70.29% <0%> (+2.97%)	34% <0%> (+1%)	⬆️
...m/alibaba/csp/sentinel/log/DateFileLogHandler.java	57.57% <0%> (+3.03%)	7% <0%> (+1%)	⬆️

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[sczyh30]

LGTM

[sczyh30]

Nice work, thanks!