Retry timestamp write to swift

[SuperSandro2000]

No description provided.

[majewsky]

Please explain via comment what the loop is doing and why.

[majewsky]

I apologize for not looking at this better the first time around. There are two main problems with this implementation:

1. On persistent error, the for-loop never terminates because errs is scoped to the loop and thus always reset to empty on each loop iteration. It will never contain more than one entry. errs needs to be allocated outside of the loop.
2. When finally failing, there is a useless sleep before that. The sleep should happen only after checking if the loop is to be terminated.

While fixing this, I refactored the retry logic into a separate function to make it stand out better, and then it just ended up so different from the original that I put it up as a separate PR -> #90