Remove existence-probe workaround in ussDeleteHandler once ufsd#9 is fixed

[mgrossmann]

Summary

ussDeleteHandler currently probes for path existence (via ufs_fopen + ufs_diropen) before calling ufs_remove() or ufs_rmdir(), because ufs_remove() returns 0 even for non-existent paths (see mvslovers/ufsd#9).

Once ufsd properly returns UFSD_RC_NOFILE for non-existent paths, this workaround can be simplified back to the original strategy:

1. Try ufs_remove() — check return code
2. If UFSD_RC_ISDIR → ufs_rmdir() or uss_recursive_delete()
3. If UFSD_RC_NOFILE → 404

Affected code

• src/ussapi.c, ussDeleteHandler — the ufs_fopen/ufs_diropen probe block

Depends on

• ufs_remove() returns 0 for non-existent paths ufsd#9