Wait for "sending notifies" for step3.zsk-prepub

Wait for "sending notifies" for step3.zsk-prepub

Commit c17ac426082b2eca802dd1b2e1bb9b4b4b291199 changed some tests to
wait for "zone_needdump" messages instead of "sending notifies", because
notifies are rate limited and "zone_needdump" happen on every change.

However, inspecting the logs, the "zone_needdump" changes happen more
than once (likely because the re-signing is done in batches):

    received control channel command 'sign step3.zsk-prepub.manual'
    zone_journal: zone step3.zsk-prepub.manual/IN (signed): enter
    zone_needdump: zone step3.zsk-prepub.manual/IN (signed): enter
    zone_journal: zone step3.zsk-prepub.manual/IN (signed): enter
    zone_needdump: zone step3.zsk-prepub.manual/IN (signed): enter
    zone_journal: zone step3.zsk-prepub.manual/IN (signed): enter
    zone_needdump: zone step3.zsk-prepub.manual/IN (signed): enter
    zone step3.zsk-prepub.manual/IN (signed): sending notifies

This means we are running the rollover step checks too fast in some
test runs.

Revert the wait for log change for the rollover-zsk-prepub test.