s3: Fix a bug in net's use of popt

s3: Fix a bug in net's use of popt

In order to add --use-ccache to net, I added another "bool opt_ccache;" to
struct net_context. popt did not like this, it took a while to figure out why.
Popt has the lines

    /* XXX Check alignment, may fail on funky platforms. */
    if (arg == NULL || (((unsigned long)arg) & (sizeof(*arg)-1)))
        return POPT_ERROR_NULLARG;

The "bool opt_ccache;" was not aligned anymore...