Temporarily modify timeout values to decrease test run times.

Recent test run data that showed that very few tests take longer than
3 minutes.  Of those that do exceed 3 minutes, most fail upon reaching
the timeout duration.

Thus, the default timeout value for all tests run in debug mode will
be 3 minutes.  This is down from 4 minutes for non-stress tests and 16
minutes for stress tests.

Specifically, this change
- decreases the timeout multiplier for debug mode from 4 to 3.
- decreases the timeout multiplier for stress tests from 4 to 1.