LU-13717 sec: support encrypted files handling in pfsck mode

LU-13717 sec: support encrypted files handling in pfsck mode

e2fsck needs to be improved in order to support encrypted files
handling in parallel fsck mode. The e2fsck_merge_encrypted_info()
function is added to merge encrypted inodes info collected from
different threads in pass1, so that it can be used in pass2.

Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: Iaf495f399e38e3ca7914b92059607d4babc1ad44
Reviewed-on: https://review.whamcloud.com/45289
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Li Dongyang <dongyangli@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>