ACCUMULO-1789 Add timeout scaling factor to tests

Slower hardware or VMs may have trouble completing tests within the timeouts
specified. This change adds a -f option to run.py to add a scaling factor
to the maxRuntime for tests, the timeout for Accumulo to shut down, and to
a specific timeout in SimpleBalancerFairness.

Signed-off-by: Eric Newton <eric.newton@gmail.com>