AbstractConnPool.java 提交记录
https://github.com/apache/httpcomponents-core/commits/4.4.x/httpcore/src/main/java/org/apache/http/pool/AbstractConnPool.java
HTTPCORE-567: fixed race condition that may cause a connection leak when the connection lease request is cancelled from another thread.
https://github.com/apache/httpcomponents-core/commit/9b5b641cd06dd883d0b72eae8a71e8a71f52729b#diff-9db2ef2f1b94de8de5d1df36b2e44a03
