The initial ->atomic_open op was carried over from the old intent code,
which was incomplete and didn't really work. Replace it with a fresh
method. In particular:
* always attempt to do an atomic open+lookup, both for the create case
and for lookups of existing files.
* fix symlink handling by returning 1 to the VFS so that we can follow
the link to its destination. This fixes a longstanding ceph bug (#2392).
Signed-off-by: Sage Weil <sage@inktank.com>
5ef50c3bec