tasks/watch_notify_same_primary: fix test for new watch/notify

It now checks for 'notify1' and 'notify2' strings, allowing it to work
on both old and new versions of rados watch command.

Signed-off-by: Sage Weil <sage@redhat.com>
Merge pull request #264 from ceph/wip-wn

tasks/watch_notify_same_primary: fix test for new watch/notify

Reviewed-by: Samuel Just <sjust@redhat.com>