Turn off ustat row count estimation by default

The initial execution of Update Statistics after loading a
table sometimes gets inaccurate HBase row count estimates.
Until the cause of this variance is determined and fixed,
the cqd controlling use of estimation has been set to OFF
by default.

Change-Id: I698f5ac8407495f890a242c82a1946a5506ceebf
Partial-Bug: #1402031