https://fedorahosted.org/sssd/ticket/453

It makes sense to keep using the boolean for access granted/denied, but
when the user/group is not found, the request would now return
ERR_ACCOUNT_UNKNOWN

https://fedorahosted.org/sssd/ticket/1713

In the simple access provider, we need to only canonicalize user names when
comparing with values in the ACL, not when searching the cache. The sysdb
searches might do a base search with a DN constructed with the username
which fails if the username is lower case.

Changes the simple access provider's interface to be asynchronous. When
the simple access provider encounters a group that has gid, but no
meaningful name, it attempts to resolve the name using the
be_file_account_request function.

Some providers (like the AD provider) might perform initgroups
without resolving the group names. In order for the simple access
provider to work correctly, we need to resolve the groups before
performing the access check. In AD provider, the situation is
even more tricky b/c the groups HAVE name, but their name
attribute is set to SID and they are set as non-POSIX

In preparation for making struct be_req opaque.

In preparation for making be_req opaque

Call it everywhere instead of directly dereferencing be_req->fn
This is in preparation of making be_req opaque.

Need to split out the function or new additions to the handler funtion will not
allow simple access tests to compile anymore.

The sysdb context is already available through the 'domain' structure.

Also remove unused sysdb_search_domgroup_by_gid()

Also remove unused sysdb_search_domuser_by_name()