If the hostname field of the ast_tcptls_session_args structure is
set (which it is for websocket client connections), that hostname
will now automatically be used in an SNI TLS extension in the client
hello.

Resolves: #713

UserNote: Secure websocket client connections now send SNI in
the TLS client hello.

(cherry picked from commit 7223dfe244d84b0168bc06ad6b4ad7e793582577)