https://fedorahosted.org/sssd/ticket/1818

I have here a LDAP user entry which has this attribute

	loginAllowedTimeMap::
	 AAAAAAAAAP///38AAP///38AAP///38AAP///38AAP///38AAAAAAAAA

In the function sysdb_attrs_add_string(), called from
sdap_attrs_add_ldap_attr(), strlen() is called on this blob, which is
the wrong thing to do. The result of strlen is then used to populate
the .v_length member of a struct ldb_val - and this will set it to
zero in this case. (There is also the problem that there may not be
a '\0' at all in the blob.)

Subsequently, .v_length being 0 makes ldb_modify(), called from
sysdb_set_entry_attr(), return LDB_ERR_INVALID_ATTRIBUTE_SYNTAX. End
result is that users do not get stored in the sysdb, and programs like
`id` or `getent ...` show incomplete information.

The bug was encountered with sssd-1.8.5. sssd-1.5.11 seemed to behave
fine, but that may not mean that is the absolute lower boundary of
introduction of the problem.

https://fedorahosted.org/sssd/ticket/1612

This patch changes the handling of ghost attributes when saving the
actual user entry. Instead of always linking all groups that contained
the ghost attribute with the new user entry, the original member
attributes are now saved in the group object and the user entry is only
linked with its direct parents.

As the member attribute is compared against the originalDN of the user,
if either the originalDN or the originalMember attributes are missing,
the user object is linked with all the groups as a fallback.

The original member attributes are only saved if the LDAP schema
supports nesting.

The original sysdb code had a strong assumption that only users from one
domain are saved in the databse, with the subdomain feature, we have
changed reality, but have not adjusted all the code arund the sysdb calls
to not rely on the original assumption.

One of the side effects of this incongrunece is that currently group
memberships do not return fully qualified names for subdomain users as they
should.

In oreder to fix this and other potential issues surrounding the violation
of the original assumption, we need to fully qualify subdomain user names.
By savin them fully qualified we do not risk aliasing local users and have
group memberhips or other name based matching code mistake a domain user
with subdomain usr or vice versa.

https://fedorahosted.org/sssd/ticket/1589

Added check for determining, whether database version is higher or
lower than expected. To distinguish it from other errors it uses
following retun values (further used for appropriate error message):
EMEDIUMTYPE for lower version than expected
EUCLEAN for higher version than expected

When SSSD or one of it's tools fails on DB version mismatch, new error
message is showed suggesting how to proceed.

To be able to efficiently store group memberships we need to know the
current memberships of a user. sysdb_initgroups() is used to read the
user entry together with all groups the user is a member of. Some of the
group attributes are kept to avoid additional lookups and speed up
further processing.

Currently sysdb_initgroups() does not return the original DN of the
group. Since it is needed to remove memberships later on it is added to
the list of requested attributes

Add a help function which returns the ldb_dn object for the base dn of
the cache.

A couple of sysdb functions used "void *" in place of a TALLOC_CTX.

The domain can be read from the sysdb object. Removing the domain string
makes the API more self-contained.