fs-metawrap: Set underlying file async only for fs_read_stream() lookups.
fs-metawrap: Set underlying file async only for fs_read_stream() lookups.

jwm/dovecot-notmuch,jwm/dovecot-notmuch,jkerihuel/dovecot,jwm/dovecot-notmuch,jwm/dovecot-notmuch,jkerihuel/dovecot,jkerihuel/dovecot,jkerihuel/dovecot,jwm/dovecot-notmuch,jkerihuel/dovecot