sharpd: Fix nexthop group name collision

sharpd: Fix nexthop group name collision

If you have two nexthop groups named
one
oneone

then the sharp daemon will treat them as the same nexthop
group.  This is because we are doign this:

static int sharp_nhg_compare_func(const struct sharp_nhg *a,
                                  const struct sharp_nhg *b)
{
        return strncmp(a->name, b->name, strlen(a->name));
}

The strlen should be the size of the array of name.

Signed-off-by: Donald Sharp <sharpd@nvidia.com>