Optimize a case in two thread call reconnect method.

[carryxyh]

Add reconnection lock to control only one thread can can reconnect method.
This will avoid problem in this case:
Thread A reconnecting, and success, then send msg.
Thread B reconnecting but invoke disconnect. Then the Thread A will send msg fail because of Thread B's disconnecting call.

The issue is here:
#944

[codecov-io]

Codecov Report

Merging #2135 into master will increase coverage by 0.06%.
The diff coverage is 0%.

@@             Coverage Diff              @@
##             master    #2135      +/-   ##
============================================
+ Coverage     54.18%   54.25%   +0.06%     
- Complexity     5092     5093       +1     
============================================
  Files           559      559              
  Lines         24935    24955      +20     
  Branches       4442     4459      +17     
============================================
+ Hits          13512    13540      +28     
+ Misses         9386     9379       -7     
+ Partials       2037     2036       -1

Impacted Files	Coverage Δ	Complexity Δ
...pache/dubbo/remoting/transport/AbstractClient.java	0% <0%> (ø)	0 <0> (ø)	⬇️
...rpc/protocol/dubbo/telnet/InvokeTelnetHandler.java	51.89% <0%> (-3.8%)	10% <0%> (-3%)
...ng/initializer/DubboWebApplicationInitializer.java
...nitializer/DubboApplicationContextInitializer.java	100% <0%> (ø)	2% <0%> (?)
...apache/dubbo/rpc/protocol/dubbo/FutureAdapter.java	64.51% <0%> (+6.45%)	3% <0%> (ø)	⬇️
...apache/dubbo/common/utils/CompatibleTypeUtils.java	72.89% <0%> (+11.78%)	30% <0%> (+1%)	⬆️
...g/spring/initializer/DubboApplicationListener.java	90.9% <0%> (+27.27%)	4% <0%> (+1%)	⬆️

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[zonghaishang]

It looks good to me

[carryxyh]

There has sth wrong about my describe of this pr.
This is one optimize when two thread call reconnect.

In old way:
Thread A call reconnect.
Thread B call reconnect. This case maybe make twice connect and twice disconnect.

In new way:
Thread A call reconnect, Thread B wait for the lock.
After Thread A finishing reconnect, Thread B will not do connect and disconnect. Because of that Thread A finish connect, this client is connected, it dose not need to reconnect again.