dcache: don't clear DCACHE_DISCONNECTED too early

DCACHE_DISCONNECTED should not be cleared until we're sure the dentry is
connected all the way up to the root of the filesystem.  It *shouldn't*
be cleared as soon as the dentry is connected to a parent.  That will
cause bugs at least on exportable filesystems.

Acked-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>