During export, between the warning stage and the final notify, we may
get cache expire messages because the replicas are sending to both us
and the new auth. This check should look for >= WARNING so that it
includes the EXPORTING states as well as the portion of WARNING after
we heard from that replica. This aligns the conditional with the
following assert such that they are properly mutually exclusive.
Fixes: #1527 Signed-off-by: Sage Weil <sage@inktank.com>