rpctls_impl.c: Fix handling of socket for daemon failure

If the client side rpc.tlsclntd is not running when a
NFS-over-TLS connection attempt is made, the socket
is left open. This results in the rpc.tlsservd daemon on
the NFS server being stuck in SSL_accept() until the
daemon is restarted.

This patch fixes this by doing soclose() on the socket
for the cases where the daemon has not acquired the
socket.

Reviewed by: glebius
Differential Revision: https://reviews.freebsd.org/D50961