Disable statistics for default installations

Disable statistics for default installations

As discussed during weekly call, with the move towards prometheus way of
monitoring policy framework components. There is no need to keep the
statistics flag turned on by default and utilize resources in processing
& storing them. Hence, turning off the flag here.
Will raise another review for OOM.

Won't cause any breakage to CSIT as we are already providing config
to enable the statistics there.

Issue-ID: POLICY-3156
Change-Id: I89962277a6b9aede713317336f776ea3ed9ffd65
Signed-off-by: Ram Krishna Verma <ram_krishna.verma@bell.ca>