Setup broke from 1.0.15 to 1.0.16

[marjoleinds]

Subject of the issue

Running the create-change-set fails after upgrading from 1.0.15 to 1.0.16.

Steps to reproduce

Our setup has an masterAccountId in the .org-formation.rc that equals our management account and moreover has a custom DefaultBuildAccessRoleName that exists in the management account. Running "org-formation create-change-set" used to work, but now fails with:
ERROR: unable to put object to s3 (bucket: organization-formation-<account_1>, key: change-sets/xxxx) User: arn:aws:sts::<account_1>:assumed-role/<account_1_role> is not authorized to perform: sts:AssumeRole on resource: arn:aws:iam::<account_1>:role/<account_2_role> (use option --print-stack to print stack)

Expected behaviour

Patch should not break existing functionality.

Actual behaviour

The command used to upload state and change-sets to account1, and that role <account_1_role> has rights to do so. Now it suddenly looks like it wants to assume the build role in the management account to upload things to s3 in the management account instead of <account_1>. This already seems strange to me, because this seems to suggest it wants to store the state-file in the management account all of a sudden.
Moreover, the error wants to assume the build-access-role in account 1 instead of in the management account, which also wouldn't make sense.