When Shepherd starts the getmail service, the TESTBOX mailbox needs to be
present, otherwise getmail fails with:
Copyright (C) 1998-2023 Charles Cazabon and others. Licensed under GNU GPL version 2.
SimpleIMAPRetriever:alice@localhost:143:
mailbox b'TESTBOX' not selectable (TESTBOX) - verify the mailbox exists and you have sufficient permissions
0 messages (0 bytes) retrieved, 0 skipped from SimpleIMAPRetriever:alice@localhost:143
* gnu/tests/mail.scm (run-getmail-test): Move the TESTBOX creation from here ...
(%getmail-os): ... to the dovecot configuration.
Change-Id: Ic6348565629c69e8b7bccf7c61460ca96850e6bd
efb910877f