EX-5021 lipe: lpcc_purge recognize pcc pin flag

EX-5021 lipe: lpcc_purge recognize pcc pin flag

lpcc_purge check pcc pin flag on lustre file and do not purge
matching cache file in PCC RO.

Change-Id: Iebbe8d1a46a9aefbecd8fd0eb1bbdf71770b0499
Signed-off-by: Lei Feng <flei@whamcloud.com>
Test-Parameters: trivial testlist=sanity-pcc
Reviewed-on: https://review.whamcloud.com/46920
Reviewed-by: Yingjin Qian <qian@ddn.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>