Fix reference to INDEX_MAKER in IndexGeneratorJob.

[gianm]

Fix reference missed in #1895

[drcrallen]

I don't think that's a "fix" so much as it is a "change hadoop to use IndexMerger"

[gianm]

@drcrallen this method was using IndexMerger before #1895, which unintentionally changed it to use IndexMaker

[drcrallen]

nooo.... that PR moved the persist method above it from maker to merger. you are now also moving the merge method from maker to merger.

[drcrallen]

https://github.com/druid-io/druid/pull/1895/files#diff-c08808f4e0bf4031ecbaac2cb044ca63L477

[gianm]

@drcrallen the intent of that PR was to remove LegacyIndexGeneratorJob and make IndexGeneratorJob behave like LegacyIndexGeneratorJob did. see also this if statement that was removed:

https://github.com/druid-io/druid/pull/1895/files#diff-0c9aca6f2536c742356ddc0bae3df945L68

"isPersistInHeap" would always be false (because it wasn't documented) so LegacyIndexGeneratorJob would always have got used. So #1895 was trying to collapse those without changing any behavior, by adjusting IndexGeneratorJob to behave like LegacyIndexGeneratorJob did. But this method got missed.

[himanshug]

👍

[drcrallen]

@gianm much better explanation, thanks!

[drcrallen]

👍 after travis