Addition of Configurable Sampling and Configurable Confirmation Retry

Addition of Configurable Sampling and Configurable Confirmation Retry

JIRA: YARDSTICK-1221

In order to increase accuracy of result the following are done :-
  - Improve Measurement Accuracy (YARDSTICK-1212)
  - Improve Sampling Interval (YARDSTICK-1219)
  - Allow 4 PROX ports to be read simultaneously (YARDSTICK-1220)

This change does the following :-
  - Stores LINE Rate statistics of Sample
  - Requires a confirmation retry before deciding to increase or
    decrease this is configurable.
  - Allows the user to disable Sampling or specify a sample interval
  - Added Code Coverage of ProxDurationRunner based on YARDSTICK-1199

Change-Id: I27242ac1849c9a2712866385b5fbc05977c71516
Signed-off-by: Daniel Martin Buckley <daniel.m.buckley@intel.com>
(cherry picked from commit 2e447af9a5a54355aa20028813660d07d1bd2e18)