HBASE-12550 Check all storefiles are referenced before splitting

Summary: If there are bugs in HDFS move and/or create we should protect against them by making sure that all files referenced end up in split daughters.

Test Plan: Unit tests cover splits pretty well

Subscribers: matteobertozzi

Differential Revision: https://reviews.facebook.net/D29373
HBASE-12550 ADDENDUM Check all storefiles are referenced before splitting
Revert "HBASE-12479 Backport HBASE-11689 (Track meta in transition) (Virag Kothari)"

This reverts commit 0a5ab37d77532a3fd068789e07b6c55522d8dbe2.
HBASE-12550 ADDENDUM Make HRegion's api not change.