Change flush defaults to encourage parallel IO and larger flushes

Based on some recent experiments with high throughput writes using YCSB[1],
these defaults make more sense for the typical throughput-oriented applications
that Kudu is currently targeting.

[1] http://getkudu.io/2016/04/26/ycsb.html

Change-Id: I1c70d9c76ed33bbfca5480e1d1f343c6dab36d3b
Reviewed-on: http://gerrit.cloudera.org:8080/3186
Tested-by: Kudu Jenkins
Reviewed-by: Jean-Daniel Cryans
(cherry picked from commit b27bb312b5f12126e3a150d0885cd9b178f42336)
Reviewed-on: http://gerrit.cloudera.org:8080/3268
Reviewed-by: Todd Lipcon <todd@apache.org>
5 files changed