bhyve: close fd in rfb

[aokblast]

Summary

cfd may still be valid after reaching the 'done' label,
especially in cases like incorrect password authentication in VNC authentication step.
To ensure the connection is properly terminated, we manually close the fd.

[aokblast]

fix unrelated modification

[markj]

usr.sbin/bhyve/rfb.c

1194

This socket is closed in the caller.

Note that double-close can be dangerous, especially in a multi-threaded program, since the fd might be reused by a different thread in between the first and second close() calls.

[aokblast]

usr.sbin/bhyve/rfb.c

1194

Emm, you are right. I have this when I using builtin vnc viewer from the MacOS and it stucks when I type a wrong password. I try to add this and it works. Maybe it is because of other reason. I would close this patch right now. Sorry for the bothering!