DAOS-16822 dfs: follow on improvement for dfs_sys_mkdir_p

[mchaarawi]

• improve performance when caching is disabled by not looking up full path each iteration.
• return ENOTDIR instead of EEXIST if a file exists instead of dir.

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[github-actions]

Ticket title is 'Add mkdir_p variant to dfs_sys API'
Status is 'In Review'
https://daosio.atlassian.net/browse/DAOS-16822

[daltonbohning]

This was intentionally returning EEXIST before to be inline with this

$ mkdir dir
$ touch file
$ mkdir dir
mkdir: cannot create directory ‘dir’: File exists
$ mkdir file
mkdir: cannot create directory ‘file’: File exists
$ mkdir -p file
mkdir: cannot create directory ‘file’: File exists

And the C API - ENOTDIR is only when a parent path does not exist
https://linux.die.net/man/3/mkdir

EEXIST
The named file exists.
ENOTDIR
A component of the path prefix is not a directory.

Thoughts?

[mchaarawi]

i should be able to change ENOTDIR To EEXISTS for the last lookup of the leaf entry. will update

[daosbuild1]

Test stage Functional Hardware Medium Verbs Provider completed with status FAILURE. https://build.hpdd.intel.com//job/daos-stack/job/daos/view/change-requests/job/PR-15569/4/execution/node/1565/log