phosphor-ldap-conf: update nslcd.conf file for OpenLdap

update the config file with "filter group (objectclass=posixGroup)"
for OpenLdap.

Change-Id: I4a0a4693294745391d58d7ee9158c75468637f36
Signed-off-by: Nagaraju Goruganti <ngorugan@in.ibm.com>
diff --git a/phosphor-ldap-config/ldap_configuration.cpp b/phosphor-ldap-config/ldap_configuration.cpp
index 6fdc511..9e918e4 100644
--- a/phosphor-ldap-config/ldap_configuration.cpp
+++ b/phosphor-ldap-config/ldap_configuration.cpp
@@ -137,6 +137,7 @@
         confData << "filter passwd (objectclass=*)\n";
         confData << "map passwd uid cn\n";
         confData << "map passwd gecos displayName\n";
+        confData << "filter group (objectclass=posixGroup)\n";
     }
     try
     {