use host scope when inserting options for a reservation

This MR changes scope_id from 1 to 3. There should never be a call to option_db_record_reservation() with something other than host because options that belong to reservations always have host scope. If the reviewer so desires, host could also be hardcoded into the function.

Only Postgres tests are impacted by this bug, but this MR changes MySQL so that the tests properly use reservation option-data as intended and not subnet option-data.

Should fix the following tests:

• test_v6_host_reservation_pgsql_hwaddrr_matching_option
• test_v6_host_reservation_pgsql_hwaddrr_matching_option_inforequest
• test_v6_host_reservation_pgsql_hwaddrr_matching_option_no_address
• test_v6_host_reservation_pgsql_option_multiple
• test_v6_host_reservation_pgsql_all_values_mac

The database results should be the same as after a reservation-add.