allow us to disable the timing output from each task but keep the final report

[ssbarnea]

Currently the timing report adds one line after each task, making the entire output much much longer and harder to read.

As an user, I want to get the timing report at the end but not to bother adding a new line for each executed task.

TASK [pyserver : install python packages globally] *****************************
Tuesday 15 March 2016  12:15:45 +0000 (0:00:19.568)       0:02:32.008 *********

The second line is not really needed but if if it could be merged into the first one it would be even better.