Try:
sysctl net.core.default_qdisc
to see which qdisc is set as default. in OpenWrt there exists /etc/sysctl.conf which you can use to change the compiled in default of fq_codel. That said, fq_codel tends to be a better all around qdisc than cake, so I would recommend to think hard, before making cake your default. (But it is a policy decision for you to make, so if you decide for your network cake to be the better default, I won't disagree, not that you should care 
)