AWS Sizing script errors out when there's no access to backup plans in linked accounts

[DamaniN]

Error:

This seems to occur when there is a payer account that is linked to the account being scanned.

[DamaniN]

To work around this issue I added the changes commit 0b3296d. This still needs to be formally investigated and fixed. The script should detect linked accounts and try to get the backup plan cost from the payer account.