Fixed UIDVALIDITY changed error when dovecot-uidlist file didn't exist but index already had UIDVALIDITY.
Fixed UIDVALIDITY changed error when dovecot-uidlist file didn't exist but
index already had UIDVALIDITY.

--HG--
branch : HEAD

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