Fix up use of pointer values in ipam and use CAS for deletion
Fix up use of pointer values in ipam and use CAS for deletion

insequent/libcalico-go,projectcalico/libcalico-go,dunjut/libcalico-go,dunjut/libcalico-go,projectcalico/libcalico-go,insequent/libcalico-go