UTIL: Add sss_create_dir()
The newly added function helps us to create a new dir avoiding a
possible TUCTOU issue.
It's going to be used by the new session provider code.
A simple test for this new function has also been provided.
Signed-off-by: Fabiano Fidêncio <firstname.lastname@example.org>
Reviewed-by: Pavel Březina <email@example.com>
Reviewed-by: Jakub Hrozek <firstname.lastname@example.org>