This warning is currently a fatal error. The code attempts
to retry the accept call, but because we don't reset sock = -1
the retry doesn't happen and it dies anyway.
Set sock = -1 so the retry attempt can happen.
"libguestfs: warning: unexpected connection from UID %d to port %d\n",
uid, null_vmchannel_sock);
close (sock);
"libguestfs: warning: unexpected connection from UID %d to port %d\n",
uid, null_vmchannel_sock);
close (sock);