DAOS-18604 dfs: EC should not be used for directories (#17573)

[mchaarawi]

• if dir-oclass is set to EC on container create, use default instead.
• daos fs set-attr of an EC oclass on directory should apply only to files. directories will be create with the default in that case.
• fix daos fs get-attr to show such changes

Steps for the author:

• Commit message follows the guidelines.
• Appropriate Features or Test-tag pragmas were used.
• Appropriate Functional Test Stages were run.
• At least two positive code reviews including at least one code owner from each category referenced in the PR.
• Testing is complete. If necessary, forced-landing label added and a reason added in a comment.

After all prior steps are complete:

• Gatekeeper requested (daos-gatekeeper added as a reviewer).

[github-actions]

Ticket title is 'daos fs set-attr unexpected behavior'
Status is 'Awaiting backport'
Labels: 'triaged'
Job should run at elevated priority (1)
https://daosio.atlassian.net/browse/DAOS-18604

[daosbuild3]

Test stage Functional Hardware Medium Verbs Provider completed with status FAILURE. https://jenkins-3.daos.hpc.amslabs.hpecorp.net//job/daos-stack/job/daos/view/change-requests/job/PR-17635/2/execution/node/1535/log