BUG-6890: Statistics-polling configuration

BUG-6890: Statistics-polling configuration

Changing the current flag to enable/disable statistics
polling.

Currently the statistics polling is controlled by the flag
is-statistics-polling-off which is off by default(value set to false).
However this logic being double-negative causes some confusion to the
end-user. Thus modifying the flag to is-statistics-polling-on and setting
it to true by default.

The associated logic involved at oyther places have been modified as
well as a part of this commit.

Change-Id: Ia9a027433611912c11ff0f3166aa6f68efdc6913
Signed-off-by: Shuva Kar <shuva.jyoti.kar@ericsson.com>