class TestSSLServer's destructor hang forever.

[jiayuehua]

when run this unit test.

./io_async_async_test --gtest_filter=AsyncSSLSocketTest.ConnectWriteReadClose

the test can't finish since on the eventbase thread that evb_ loop not exit even ~TestSSLServer() call:

evb_.runInEventBaseThread([&]() { socket_->stopAccepting(); });

so thread_.join(); hang forever.

\folly\io\async\test\TestSSLServer.h

Also there's ODR violation for io_async_async_test, for example class ReadCallback is defined in two files: folly\io\async\test\AsyncSocketTest.h and
folly\io\async\test\AsyncSSLSocketTest.h. May be should split io_async_async_test into two test, one for AsyncSocket related and another for AsyncSSLSocket related.