ipasam: improve SASL bind callback

SASL bind callback due to refactoring was referencing local variable which
didn't exist all the time. Fix that by including a copy of service principals
into ipasam long term private struct.

Rework ccache handling to avoid re-initing every time callback is called

install/share/smb.conf.template

@@ -18,7 +18,6 @@ ldap suffix = $SUFFIX
 ldap user suffix = cn=users,cn=accounts
 ldap group suffix = cn=groups,cn=accounts
 ldap machine suffix = cn=computers,cn=accounts
-ipasam:principal = cifs/$FQDN@$REALM
 rpc_server:epmapper = external
 rpc_server:lsarpc = external
 rpc_server:lsass = external