r3563: During a typical logon a modern workstation makes a lot of anonymous session

r3563: During a typical logon a modern workstation makes a lot of anonymous session
setups on its way to open a pipe. This gets rid of many round-trips to the
LDAP server during logon by setting up the server_info_guest once and not
asking the LDAP server and nss every time. Make sure that the ldap connection
is reopened in the child. (I did not look at the sql backends.)

Volker
(This used to be commit 3298f6105e6a88c9390cac02245c8f2eee1e5046)