EX-8466 tests: limit 'cmp' output in sanity-pcc.sh

EX-8466 tests: limit 'cmp' output in sanity-pcc.sh

Limit the number of lines printed by 'cmp' when there is an error
comparing two files.  Often the files are multiple MB in size, and
printing 1-32M lines of output when the test fails is not useful.

Instead, print the first 66000 lines of output by default, which is
enough to see a full 64KiB plus some lines to see if more than 64KiB
of data is incorrect.  This is controlled by the CMP_LINES variable.

Test-Parameters: trivial testlist=sanity-pcc
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I80f4d5d3460d531ab63788185a2c88e79415a801
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/53239
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alex Deiter <alex.deiter@gmail.com>
Reviewed-by: Qian Yingjin <qian@ddn.com>