Setup_host.sh retry docker image pull bug

[Jacob Freck]

This line in setup_host.sh is invalid bash:

aztk/aztk/node_scripts/setup_host.sh

Line 49 in 72c7833

 sleep $i**2; 

As a result, image pull retries never fire. Arithmetic should be enclosed in double parenthesis.

[mmduyzend]

Also another line in the same file:

aztk/aztk/node_scripts/setup_host.sh

Line 69 in 72c7833

 sleep $i**2;