lib-storage: Set MAILBOX_SELECT/NONEXISTENT for namespace prefix even if no flags are wanted. This fixes doveadm commands attempting to access such nonexistent mailbox prefixes.
lib-storage: Set MAILBOX_SELECT/NONEXISTENT for namespace prefix even if no flags are wanted.
This fixes doveadm commands attempting to access such nonexistent mailbox
prefixes.

dscho/dovecot,dscho/dovecot,dscho/dovecot,dscho/dovecot,dscho/dovecot