SSL related: TLSv1, remove call CRYPTO_mem_leaks(), evbuffer_copyout() to evbuffer_drain()

[kisoo-han]

We found frequent abnormal shutdown of 'cub_manager' process, and we know that it downs
in the middle of 'OpenSSL library (openssl-1.0.1-alpha). We are going to replace it with
openssl-1.1.0e-stable (January 2017).

This is preliminary works to do that. Works include:

• change possible memory leak codes
• change default SSL protocol from SSLv3 to TLSv1
• replace evbuffer_copyout() calls to evbuffer_drain()
• remove code calls 'CRYPTO_mem_leaks()', it was removed in openssl-1.1.0e