https://pagure.io/SSSD/sssd/issue/3571

• get user1 to LDAP
• start sssd
• query getent passwd -s sss user1 (so we will be sure that user is in memory cache)
• read seed and hash_size from header of memory cache (they are needed to calculation of hash
• estimate length of entries stored in mmap cache for user1 (approximately getent passwd -s sss alcik | wc -c) But we can use hardcoded number e.g. 128
• generate hash for "user1"
• generate the same hash as in previous step from random ASCII string with length calculated in previous step (RANDOM_STRING)
• add new user (RANDOM_SRING) into LDAP with random string generated in previous step.
• query for newly added user getnet passwd -s sss $RANDOM_STRING
• stop sssd
• ensure that user1 and $RANDOM_STRING are properly stored in memory cache. (entries will be returned even though sssd is stopped)