Modifying testr conf to suppress output

Testr pumps out a lot of output to the screen even
with successful tests. Other OpenStack projects
solve this by modifying their testr config to force
stdout and stderr capture similar to other testing
frameworks. For this change, I have copied how
Nova handles this.

Change-Id: Ie6fb60585a632e09fef068f768c6b6fde10017f0
Merge "Modifying testr conf to suppress output"