Add some delay on loop on initial setup or when indexers are offline

[sondreb]

On the initial setup and/or when indexers are offline, the indexer process will run in a loop without any delays. This takes up a lot of compute resources on the devices.

The issue is that get indexer URL will return empty URL if there are no indexers online, and the completed status is set to false, so it will continue to run until indexers is online. We can either sleep for a while, or we can have some limit on how many loops is acceptable. Main issue with counting loops, is that completed is used for very large wallets and is an indicator that scan is not complete yet, so we don't want the value to be too low and create issues for large wallets.