Send the first DHCPv6 message with a delay to avoid synchronization.

Per RFC8415 section 18.2.1 the first Solicit message from the client
on the interface should be delayed by a random amount of time between
0 and SOL_MAX_DELAY(1s). Send the first message with a delay in the
PacketRetransmitState, the delay can be 0, depends on the substate.

Bug: 260934173
Test: TH
Change-Id: If5aeaa0118515d9de3134c636871a8771cf0b148
1 file changed