Add environmental variables to test.conf

This commit adds environmental variables to .testr.conf to disable
testr capturing STDOUT and STDERR by default. So now STDOUT and
STDERR will print immediately by default when using testr. It also
adds a default 250 sec timeout for tests. If a test takes longer than
this it will fail.

Change-Id: I32d8b1a856f6e7932d16b1464553e9c25fbc3cfc
Merge "Add environmental variables to test.conf"