network: do not request DHCP addresses configured on checking prefix delegation

network: do not request DHCP addresses configured on checking prefix delegation

This does not change anything for DHCPv4, as a DHCPv4 address is always
requested anyway. However for DHCPv6, the client may not request IA_NA
addresses by UseAddress=no, or even if it is requested, the server may
not provide any IA_NA addresses. Even in such cases, here the check is
for delegated prefixes, hence it is not necessary to check if DHCPv6
IA_NA addresses are configured.

Fixes a bug introduced by 195b83edf852f4e40e0d3a3b630cde97c84d77ba.

Fixes #31349.