rpctls_impl.c: Fix handling of daemon failure

[rmacklem]

Summary

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.

It is still possible for a broken client to get the
rpc.tlsservd daemon stuck. This will be addressed
in a separate commit.

Test Plan

Tested by doing repeated NFS-over-TLS mount
attempts with both the daemon running and not
running.

[glebius]

sys/rpc/rpcsec_tls/rpctls_impl.c

234

The comment contradicts the fact that we did RB_REMOVE() two lines above.

[glebius]

I clicked on "Accept", trusting your expertise. The change looks correct, with small comment nit. But I didn't test it. And to be fair the gist of the code already washed out of my L3 brain cache :)