LU-15064 tests: sanity-sec test_58 must read its own dir

LU-15064 tests: sanity-sec test_58 must read its own dir

sanity-sec test_58 should restrict file listing to its own
directory, and not try to list content of the entire Lustre tree.
This is useless for the purpose of the test, and exposes to unclean
remnants from previous tests.

Test-Parameters: trivial
Test-Parameters: testlist=sanity-sec env=ONLY=58
Fixes: 1faf54e8bf ("LU-14989 sec: access to enc file's xattrs")
Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: Ic9ab0860da0ab86355a207ad9d50feb3975adf68