pkcs11: properly fall back to thread-unsafe module init

pkcs11: properly fall back to thread-unsafe module init

The PKCS#11 module initialization logic introduced in
aa5f15a872e62e54abe58624ee393e68d1faf689 first attempts to initialize
the module with CKR_NEED_TO_CREATE_THREADS|CKF_OS_LOCKING_OK, which
may return either CKR_CANT_LOCK or CKR_NEED_TO_CREATE_THREADS, where
the latter was previously treated as a hard error. This fixes it and
also makes the second attempt to not supply any flags.

Signed-off-by: Daiki Ueno <ueno@gnu.org>