Enter the net epoch when traversing a list of interfaces. For that
split the linux_ioctl_socket() function on two counterparts, where
the linux_ioctl_socket_ifp() intended to use in the net epoch as it
need a reference to the interface, while the linux_ioctl_socket()
function is left as is, it calls sys_ioctl() without touching in/out
values.
Due to structures ifreq, sockaddr difference between FreeBSd and Linux
the linux_ioctl_socket_ifp() calls kern_ioctl() directly, converting
in and out values to FreeBSD and to Linux accordingly.
Finally, modify the ifname_linux_to_bsd() to return error code, not
an unstable reference to the interface.