Fix binderThroughputTest -m option

The -m option allows the user to specify the estimated
max latency to calibrate buckets used for percentile
calculations. The option didn't work because the
time_per_bucket was not being set so the default value
was used.

Test: verified correct -m operation
Bug: 65052581
Change-Id: I96d6ba0271edaffda0bd9cccfef5d559d3bf111c
Signed-off-by: Todd Kjos <tkjos@google.com>