memory leak in butil::ObjectPoolAllocator

[live4thee]

Describe the bug (描述bug)

When using butil::ObjectPoolAllocator to construct butil::MPSCQueue. The returned pointer will be accidentally saved in a object pool of void pointers.

To Reproduce (复现方法)

Construct butil::MPSCQueue with butil::ObjectPoolAllocator, and check memory consumption.

Expected behavior (期望行为)

No memory leak.

Versions (各种版本)
OS: ALL supported OS.
Compiler: ALL supported compiler.
brpc: bRPC version after MPSQ was introduced.
protobuf: ALL supported version.

Additional context/screenshots (更多上下文/截图)