If INBOX is a substring of already added path, don't assert-crash. Also fixed handling cases where parent directory was added while its multiple children were already added (probably never happened).
If INBOX is a substring of already added path, don't assert-crash. Also
fixed handling cases where parent directory was added while its multiple
children were already added (probably never happened).

Distrotech/dovecot,Distrotech/dovecot,Distrotech/dovecot,Distrotech/dovecot,Distrotech/dovecot