Update makelogs to not use _default_ mapping

[rhoboat]

Caused by elastic/elasticsearch#29165
Symptom:

☁  Mar 26 12:07:18  kibana [master] ⚡ node scripts/makelogs.js
Generating 14000 events from 2018-03-25T00:00:00Z to 2018-03-27T23:59:59Z
creating index template for "logstash-*"
Error: [illegal_argument_exception] The [default] mapping cannot be updated on index [YyGgqqJGRQ2FvQo5dyddrA]: defaults mappings are not useful anymore now that indices can have at most one type.
    at respond (/Users/archana/Development/apps/elastic/versions/master/kibana/node_modules/elasticsearch/src/lib/transport.js:307:15)
    at checkRespForFailure (/Users/archana/Development/apps/elastic/versions/master/kibana/node_modules/elasticsearch/src/lib/transport.js:266:7)
    at HttpConnector.<anonymous> (/Users/archana/Development/apps/elastic/versions/master/kibana/node_modules/elasticsearch/src/lib/connectors/http.js:159:7)
    at IncomingMessage.bound (/Users/archana/Development/apps/elastic/versions/master/kibana/node_modules/elasticsearch/node_modules/lodash/dist/lodash.js:729:21)
    at emitNone (events.js:111:20)
    at IncomingMessage.emit (events.js:208:7)
    at endReadableNT (_stream_readable.js:1055:12)
    at _combinedTickCallback (internal/process/next_tick.js:138:11)
    at process._tickCallback (internal/process/next_tick.js:180:9)

[rhoboat]

Solved by elastic/makelogs#41
and #17451