test/libcephfs: put inodes after lookup

test/libcephfs: put inodes after lookup

Otherwise, the client umount will hang due to inability to trim the
inodes looked up using the low-level interface. This results in slow-op
warnings and an eviction:

	2021-09-11T17:23:31.097+0000 7f99c3522700  0 log_channel(cluster) log [WRN] : evicting unresponsive client smithi176 (9756), after 303.924 seconds
	2021-09-11T17:23:31.097+0000 7f99c3522700 10 mds.0.server autoclosing stale session client.9756 172.21.15.176:0/3891214934 last renewed caps 303.924s ago

From: /ceph/teuthology-archive/yuriw-2021-09-11_16:21:09-smoke-pacific-distro-basic-smithi/6385038/remote/smithi175/log/ceph-mds.b.log.gz

Fixes: https://tracker.ceph.com/issues/52572
Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>