LU-12275 sec: encryption with different client PAGE_SIZE

LU-12275 sec: encryption with different client PAGE_SIZE

In order to properly handle encryption/decryption on clients that have
a PAGE_SIZE != LUSTRE_ENCRYPTION_UNIT_SIZE (typically aarch64/ppc64),
a few adjustements are necessary:
- when encrypting, do not proceed with PAGE_SIZE as encryption length.
  Instead, round up to a multiple of LUSTRE_ENCRYPTION_UNIT_SIZE.
  On aarch64/ppc64, it avoids encrypting way beyond
  LUSTRE_ENCRYPTION_UNIT_SIZE when the page is not full.
- when decrypting, do not proceed with PAGE_SIZE as decryption length.
  Instead, do LUSTRE_ENCRYPTION_UNIT_SIZE length at a time. It enables
  proper detection of 'all 0s' sent by servers for content beyond file
  size.

Regarding tests, add sanity-sec test_53 to exercise encryption from
clients with different PAGE_SIZE.
The trick to achieve this with AT is to expect the client to have 64KB
PAGE_SIZE, and the servers to have 4KB PAGE_SIZE, and then mount a
client from the MDS node.
This also means code running on server side needs to have client
encryption support enabled, so CentOS/RHEL 8 at least.

Test-Parameters: trivial
Test-Parameters: clientarch=aarch64 clientcount=1 clientdistro=el8.1 serverdistro=el8.1 testlist=sanity-sec env=ONLY="36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 52 53" fstype=ldiskfs mdscount=2 mdtcount=4
Test-Parameters: clientarch=aarch64 clientcount=1 clientdistro=el8.1 serverdistro=el8.1 testlist=sanity-sec env=ONLY="36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 52 53" fstype=zfs mdscount=2 mdtcount=4
Test-Parameters: clientarch=x86_64 clientcount=1 clientdistro=el8.1 serverdistro=el8.1 testlist=sanity-sec env=ONLY="36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 52 53" fstype=ldiskfs mdscount=2 mdtcount=4
Test-Parameters: clientarch=x86_64 clientcount=1 clientdistro=el8.1 serverdistro=el8.1 testlist=sanity-sec env=ONLY="36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 52 53" fstype=zfs mdscount=2 mdtcount=4
Test-Parameters: clientdistro=el8.1 testlist=sanity-sec env=ONLY="36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52" mdscount=2 mdtcount=4
Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: Iee4b4d9e70c2e8c8e12061c39400cf6a8c03bac3
Reviewed-on: https://review.whamcloud.com/39315
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Wang Shilong <wshilong@whamcloud.com>