HBASE-12110 Fix .arcconfig

Summary: Not many people are currently using arc but it's a nice tool for the developers who are used to it. Since it's already there let's make it work.

Test Plan: If this works then it's tested.

Differential Revision: https://reviews.facebook.net/D24075
Merge remote-tracking branch 'remotes/origin/0.98' into 0.98