HBASE-12198 Fix the bug of not updating location cache

Summary:  # Clear the cache of the server when failed

Test Plan: Add testcase `TestHTableMultiplexerFlushCache` to reproduce the bug.

Differential Revision: https://reviews.facebook.net/D24603

Signed-off-by: Elliott Clark <elliott@fb.com>
Signed-off-by: Elliott Clark <eclark@apache.org>

Amending-Author: Andrew Purtell <apurtell@apache.org>