ofs: correct an error message
ofs: correct an error message

When this was specific to the ports, it mentioned the TCP/IP stack.
Now that it is more general, it should mention the context.

Signed-off-by: David Scott <63c9eb0ea83039690fefa11afe17873ba8278a56@docker.com>

samoht/vpnkit,djs55/vpnkit,djs55/vpnkit,djs55/vpnkit