add jitter instead of scaling by jitter

[nalbion]

It's possible for a series of random numbers to be all 0, more feasible for them to be all close to zero.

Multiplying by ri would yield:

• 0 * 1 = 0
• 0 * 2 = 0
• 0 * 4 = 0
• 0 * 8 = 0

To avoid this, jitter should be added:

• 0 + 1 = 1
• 0 + 2 = 2
• 0 + 4 = 4
• 0 + 8 = 8

[lucix-aws]

The calculation for delay here is standardized across SDKs in the "standard" retry strategy, it's not something we can change.