fix: failure-detector: Choose random timeout from [0,3mu]

[akiradeveloper]

To get average distance of 1, we need to get two random numbers from range [0,3]. I proved it with a tiny experiment.

import random

N = 1000000
sum = 0
for i in range(0,N):
  x = random.uniform(0.0, 3.0)
  y = random.uniform(0.0, 3.0)
  sum += abs(x-y)
print(sum/N)

 % python3 rand-width.py
1.0004715053424982