kclient: do not recurse into truncate|invalidate pages
kclient: do not recurse into truncate|invalidate pages

A single open O_TRUNC on a file dirty pages would

	-> truncate
		-> put_wrbuffer_refs
			-> check_caps
				-> invalidate ... and deadlock

So, do not invalidate here if we have a pending truncate (which
remains elevated until after the truncate finishes).

ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph