LU-17076 orr: take a ref after lookup_get_insert_fast()

LU-17076 orr: take a ref after lookup_get_insert_fast()

We need to take a reference on all existing object returned by
nrs_orr_res_get(). Otherwise, the object could be freed before
nrs_orr_res_put().
Therefore, a ref should be taken if
rhashtable_lookup_get_insert_fast() returns an existing object.

This avoids the following use-after-free in sanityn test_77c:

ptlrpc_nrs_req_stop_nolock+0x3b/0x150
ptlrpc_server_finish_active_request+0x2b/0x140 [ptlrpc]
ptlrpc_server_handle_request+0x40e/0xc00 [ptlrpc]
ptlrpc_main+0xc8c/0x1680 [ptlrpc]
kthread+0xd1/0xe0
ret_from_fork_nospec_begin+0x21/0x21

Fixes: 42bf5f7 ("LU-8130 nrs: convert NRS ORR/TRR to rhashtable")
Test-Parameters: fstype=zfs testlist=sanityn env=ONLY=77c,ONLY_REPEAT=100
Test-Parameters: fstype=zfs testlist=sanityn env=ONLY=77c,ONLY_REPEAT=100
Test-Parameters: fstype=zfs testlist=sanityn env=ONLY=77c,ONLY_REPEAT=100
Signed-off-by: Etienne AUJAMES <eaujames@ddn.com>
Change-Id: I267287a1075ee91019d3a4492b57f272a4b0cadd
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/52295
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Alexander Boyko <alexander.boyko@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>