the total usd balance doesn't properly update, when the balance of one of the wallet changes

[dreacot]

• the total usd balance doesn't properly update, when the balance of one of the wallet changes, it only updates when going to settings page and returning

• often times the selected exchange rate resets to none

[ukane-philemon]

often times the selected exchange rate resets to none

This happens when we fail to get a rate from a selected source after three concurrent API calls... I saw that somewhere. Not sure what the correct behaviour should be but I guess we can:

1. Use stall data until we are able to get a rate or the user changes to another provider
2. Give more time before we disable the provider and reset to none.

[dreacot]

if a default had been selected before, i don't think we need to keep checking again when the app is opened