BOOTP hook doesn't work

Although the system tests have just started and there are no complete results available yet, @wlodek reported the packet is being dropped due to missing option 53.

 DEBUG [kea-dhcp4.packets/4288] DHCP4_BUFFER_RECEIVED received buffer from 0.0.0.0:68 to 255.255.255.255:67 over interface enp0s9
 DEBUG [kea-dhcp4.callouts/4288] HOOKS_CALLOUTS_BEGIN begin all callouts for hook buffer4_receive
 DEBUG [kea-dhcp4.bootp-hooks/4288] BOOTP_ADDED_CLASS added BOOTP class to a BOOTP query: [hwtype=1 ], cid=[no info], tid=0x0
 DEBUG [kea-dhcp4.callouts/4288] HOOKS_CALLOUT_CALLED hooks library with index 1 has called a callout on hook buffer4_receive that has address 0x7f45f97dedf0 (callout duration: 0.072 ms)
 DEBUG [kea-dhcp4.callouts/4288] HOOKS_CALLOUTS_COMPLETE completed callouts for hook buffer4_receive (total callouts duration: 0.072 ms)
 DEBUG [kea-dhcp4.options/4288] DHCP4_BUFFER_UNPACK parsing buffer received from 0.0.0.0 to 255.255.255.255 over interface enp0s9
 DEBUG [kea-dhcp4.eval/4288] EVAL_DEBUG_MEMBER Checking membership of 'BOOTP', pushing result 'true'
 DEBUG [kea-dhcp4.eval/4288] EVAL_DEBUG_NOT Popping 'true' pushing 'false'
 DEBUG [kea-dhcp4.options/4288] EVAL_RESULT Expression DHCP evaluated to 0
 INFO  [kea-dhcp4.bad-packets/4288] DHCP4_PACKET_DROP_0009 [hwtype=1 08:00:27:6d:ee:67], cid=[no info], tid=0x12019719: Option 53 missing (no DHCP message type), is this a BOOTP packet?