LU-10499 tests: disable metadata_csum_seed for pcc cache device

LU-10499 tests: disable metadata_csum_seed for pcc cache device

latest e2fsprogs enable metadata_csum_seed feature when mkfs.ext4
a device, which is used in pcc test as a cache device. Such a ext4
fs cannot be mounted on an old kernel of el7. So disable this
feature for pcc cache device if it is detected in sanity-pcc test.

EX-7596 tests: don't fail if metadata_csum_seed unset

Fix logic in the sanity-pcc cache filesystem setup.  With mke2fs
1.47.0-wc1 it enabled metadata_csum_seed unconditionally, but it
caused problems on el7.9 kernels. In 1.47.0-wc2 it disabled that
feature, caused the check for removing the feature to fail.

Since metadata_csum_seed has been available since 1.44.2 it
shouldn't be a problem to force it off duing mke2fs.
Was-Change-Id: Ic04ab4043981dc9b5c32e01c4aa85be343e3f3f8

EX-6826 tests: wait before unmounting pcc device if busy

wait at most 10 seconds before unmounting pcc device
if it is busy.
Was-Change-Id: I77ec018d33d14af99bdc5d5c5c94c8fa0dafdb61

EX-bug-id: EX-7596 EX-6826
Test-Parameters: trivial testlist=sanity-pcc clientdistro=el8.10
Signed-off-by: Lei Feng <flei@whamcloud.com>
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I2ef3ff27b49fb479ec348b742cf614a43321813b
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/54486
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>