Revision 1338809

[HBASE-5867] Improve Compaction Throttle Default

Summary:
We recently had a production issue where our compactions fell
behind because our compaction throttle was improperly tuned and
accidentally upgraded all compactions to the large pool. The default
from HBASE-3877 makes 1 bad assumption: the default number of flushed
files in a compaction. MinFilesToCompact should be taken into
consideration. As a default, it is less damaging for the large thread
to be slightly higher than it needs to be and only get timed-majors
versus having everything accidentally promoted.

Test Plan:  - mvn test

Reviewers: JIRA, Kannan, Liyin
Reviewed By: Kannan
CC: stack

Differential Revision: https://reviews.facebook.net/D2943