dhcp_server: T6031: DHCP Option Failures - windows-static-route (#4183)

In "option-def" parameter "record-types" field is an array of uint8 in format "<netmask>, <network-byte1>, <network-byte2>, <network-byte3>, <router-byte1>, <router-byte2>, <router-byte3>" where <network-byte3> with the value 0 is omitted, so the minimal length of array is 7 (e.g. for routing 10.1.0.0/16 via 10.1.6.4 "record-types": "16,10,1,10,1,6,4")