Changed default retry_delay_multiplicand_max to fix Kernel.rand error

In rbx, Kernel.rand(x..y) must have `y-x > 0` or it throws an ArgumentError.

This is caused by ExponentialBackoff having its max & min for randomization both 1.0. Fixed by making the max default to 1.1.

```
> RUBY_ENGINE
 => "rbx"
> RUBY_VERSION
 => "2.1.0"
> rand(1.0..1.0)
ArgumentError: invalid argument - 0.0
	from kernel/common/random.rb:39:in `random'
	from kernel/common/random.rb:72:in `random_range'
	from kernel/common/random.rb:36:in `random'
	from kernel/common/kernel.rb:669:in `rand'
	from (irb#1):6
	from kernel/common/block_environment.rb:53:in `call_on_instance'
	from kernel/common/eval.rb:176:in `eval'
	from kernel/common/kernel.rb:460:in `loop'
	from kernel/bootstrap/proc.rb:20:in `call'
	from kernel/common/throw_catch.rb:30:in `catch'
	from kernel/common/throw_catch.rb:8:in `register'
	from kernel/common/throw_catch.rb:29:in `catch'
	from kernel/bootstrap/proc.rb:20:in `call'
	from kernel/common/throw_catch.rb:30:in `catch'
	from kernel/common/throw_catch.rb:8:in `register'
	from kernel/common/throw_catch.rb:29:in `catch'
	from kernel/bootstrap/proc.rb:20:in `call'
	from kernel/bootstrap/thread.rb:391:in `__run__'rbx-2.2.7 :007 > rand(1.0..1.1)
```