fix #2560, use target/test-classes as the basedir

[diecui1202]

What is the purpose of the change

fix #2560, use target/test-classes as the basedir

Brief changelog

XXXXX

Verifying this change

XXXXX

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[codecov-io]

Codecov Report

Merging #2563 into master will decrease coverage by 0.04%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #2563      +/-   ##
============================================
- Coverage     54.98%   54.93%   -0.05%     
+ Complexity     5278     5276       -2     
============================================
  Files           573      573              
  Lines         25538    25538              
  Branches       4531     4531              
============================================
- Hits          14041    14030      -11     
- Misses         9396     9403       +7     
- Partials       2101     2105       +4

Impacted Files	Coverage Δ	Complexity Δ
...ache/dubbo/remoting/p2p/support/AbstractGroup.java	45.45% <0%> (-11.37%)	7% <0%> (-1%)
...onfig/spring/extension/SpringExtensionFactory.java	75.86% <0%> (-10.35%)	11% <0%> (ø)
...e/dubbo/remoting/transport/netty/NettyChannel.java	57.5% <0%> (-8.75%)	19% <0%> (-2%)
...org/apache/dubbo/rpc/filter/ActiveLimitFilter.java	77.77% <0%> (-5.56%)	5% <0%> (-1%)
...bo/remoting/transport/netty/NettyCodecAdapter.java	53.12% <0%> (-1.57%)	3% <0%> (ø)
.../java/org/apache/dubbo/config/ReferenceConfig.java	50.35% <0%> (-0.72%)	42% <0%> (ø)
...apache/dubbo/rpc/protocol/dubbo/DubboProtocol.java	59.16% <0%> (+0.83%)	31% <0%> (+1%)	⬆️
.../dubbo/remoting/transport/netty4/NettyChannel.java	62.35% <0%> (+1.17%)	23% <0%> (+1%)	⬆️
...dubbo/rpc/protocol/dubbo/CallbackServiceCodec.java	78.67% <0%> (+1.47%)	29% <0%> (ø)	⬇️
...ubbo/rpc/protocol/dubbo/ChannelWrappedInvoker.java	41.66% <0%> (+4.16%)	3% <0%> (ø)	⬇️
... and 1 more

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