LU-12275 tests: skip new nodemap params on old MGS

LU-12275 tests: skip new nodemap params on old MGS

Skip setting forbid_encryption and readonly_mount parameters on old
MGSes that do not support these options.  Otherwise test_61 failures
are seen during interop testing.  Running test_36 would also fail in
this case, except that it is already skipped due to encryption checks.

Lustre-change: https://review.whamcloud.com/49828
Lustre-commit: TBD (from 74c9b1f6e4d5b1fbbd615b87fb7c62c0fcb1a727)

Test-Parameters: trivial testlist=sanity-sec
Fixes: 598c48707c ("LU-12275 tests: exercise file content encryption/decryption")
Fixes: e7ce67de92 ("LU-15451 sec: read-only nodemap flag")
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I94f2e2f609927fea618a3a22f103bd32ae3ebbe5
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/49829
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>