Corrections in Python wrappers

Management of file descriptors was leaking. The cryptfd was closed
by the tlspool_starttls() call or TLS Pool but also by Python, for
instance when garbage collecting the cryptfd. This allowed closing
the same socket twice or, more accurately put, closing of the same
file descriptor number. An intermediate process might have opened
another stream with the same number, and seen it closed. Yet an
other process might have opened it once again and receive spurious
information from the stashed file descriptor in, say, the syslog()
API or Python sockets.