Add debugging log to see if DHCPv6 client sends Renew/Rebind message.

Based on current implementation, it's possbile for DHCPv6 client to skip
renew/rebind message transmission if there are no renewable prefixes in
the last Reply message. Add debugging log there to confirm if DHCPv6
client has sent Renew/Rebind message or not.

Bug: 332827141
Test: TH
Change-Id: Iec08754ada22374f322f6b4ee67ccf28110284cd
1 file changed