- Remove the printf support leaving the direct printk support configured
with TESTS_USE_PRINTK and all other output goes via a buffered vsniprintf
call to printk.
- Control the test's single init for functions and global data with
TEST_INIT and not CONFIGURE_INIT. They are now separate.
Updates #3170.
Use '*" to disable shell login instead of '!' according to the Linux man
page. Use getpwnam_r() instead of getpwnam(). Do not access the user
environment directly. Update the user environment only after a
successful login check.