Why pfcp_add_del_v4_teid is not used for add?

[hesingh]

I see use of pfcp_add_del_v4_teid (v4_teid, sx, 0); for delete as shown on the line below.

https://github.com/travelping/upg-vpp/blob/ca2791c3f9d2645b67102bf295609c0d9ce529de/upf/upf_pfcp.c#L991

For better code maintenance, pfcp_add_del_v4_teid() should be used to add as well, but the code does not. Instead the code uses hash_set()