[FIX] Workaround for missing confirmations

This will fix issues with those coins that don't track confirmations for
blocks inside the getblock RPC call. It will try to fallback to the
transactions confirmations and insert those instead.

Fixes #1823 as mentioned by @ice00 - Thanks for that!
Merge pull request #1876 from MPOS/block-confirmations

[FIX] Workaround for missing confirmations