Retry IOException and HttpIOException exceptions

[jakejscott]

Having a look into #266

[bill-poole]

The detection logic is checking for IOException, HttpIOException or SocketException, but HttpIOException derives from IOException, so it should be possible to just check for IOException and SocketException.

[firenero]

Thanks for the PR @jakejscott. I've made several changes before merging:

• Propagate IO exceptions instead of wrapping them into DdbException. Since these errors are not caused by DDB itself I think it's fair to throw after retries.
• Increased retries count to 10 from default 5 just in case.
• Removed explicit handling of HttpIoException since it implicitly handled by IoException (thanks @bill-poole for spotting it).

[jakejscott]

Thank you so much! 😊