609255 - fix coverity Defect Type: Memory - illegal accesses issues

https://bugzilla.redhat.com/show_bug.cgi?id=609255

12220 UNINIT Triaged Unassigned Bug Minor Fix Required
create_NSDS50ReplicationExtopPayload() ds/ldap/servers/plugins/replication/repl_extop.c

Comment:
unlikely to cause a problem, but we should init sdn to NULL

ldap/servers/plugins/replication/repl_extop.c

@@ -115,7 +115,7 @@ create_ReplicationExtopPayload(const char *protocol_oid,
     Object  *repl_obj, *ruv_obj = NULL;
 	Replica *repl;
     RUV *ruv;
-    Slapi_DN *sdn;
+    Slapi_DN *sdn = NULL;
 
 	PR_ASSERT(protocol_oid != NULL || send_end);
 	PR_ASSERT(repl_root != NULL);