A crash would occur if an SSL socket was not shut down before
`gc_deinit()`.
I do not fully understand the root cause, but some object deinitialization
/ deallocation prior to `gc_deinit` leaves the SSL object in an
inconsistent state.
Rather than resolve the root cause, instead ensure that the closing of
the user socket also closes the SSL socket.
Closes: #6502
7583ccad2a