LU-10499 pcc: get PCC state for a file without opening itself

LU-10499 pcc: get PCC state for a file without opening itself

Originally to get PCC state for a given file, the user needs to
open the file and then get the current PCC state of the file via
the file handle. After that, close the file.

If the file is met the predefined condition of auto prefetching
into PCC at the open time, "lfs pcc state" command on the file
will attach the file into PCC cache. This may be not the intention
of the user.

In this patch, we rework the "lfs pcc state" command. It always
open the parent directory, and then do the lookup by name/FID
without open the file itself to get the PCC state.

EX-5358 pcc: remove realpath() from lfs_pcc_state()

Before Ubuntu 20.04, realpath() executes lstat() for each
component of the path. If the file is still valid cached on PCC
device with the layout generation unchanged, the Lustre file will
be auto re-attach during the stat() call in the Lustre kernel.
This may result in misunderstanding for the operation "lfs pcc
state" on a file that has already detached but still valid cached
on PCC according to the unchanged layout generation.

This problem exposes on the newer Ubuntu 22.04 in which realpath()
executes readlink() for each component of the path instead of
lstat():
readlink("/mnt", 0x7fffd5760800, 1023)  = -1
readlink("/mnt/lustre", 0x7fffd5760800, 1023) = -1
readlink("/mnt/lustre/sanity-pcc.f15", 0x7fffd5760800, 1023) = -1
Was-Change-Id: I50ae46a1e952a3faaf0d7a7293579e239156d6d3

LU-16030 pcc: enlarge PCC backend size for sanity-pcc script

In this patch, it removes realpath() from lfs_pcc_state() to avoid
this misunderstanding behavior for the command: $LFS pcc state.
And it also fixes the test scripts sanity-pcc: test_15, test_16,
test_27, test_39.
Was-Change-Id: Ib19f01ed054cb6c9eecceabea1f1da72dea0b113

EX-bug-id: EX-2455 EX-5358 LU-16030
Test-Parameters: clientcount=3 testlist=sanity-pcc,sanity-pcc,sanity-pcc
Signed-off-by: Qian Yingjin <qian@ddn.com>
Change-Id: I310a7e73dc6c0f4318dc27df2e02ecf6559ee5b4
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/54372
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Li Xi <lixi@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>