Caused by HADOOP-16830 and HADOOP-17271.
Fixes tests which fail intermittently based on configs and
in the case of the HugeFile tests, bulk runs with existing
FS instances meant statistic probes sometimes ended up probing those
of a previous FS.
Contributed by Steve Loughran.
Change-Id: I65ba3f44444e59d298df25ac5c8dc5a8781dfb7d