Basic Authentication Plugin is not working in solr 6.4

I am try to enable Basic Authentication Plugin in solr 6.4.0 using the below configuration

Step-1 Creates security.json file in solr location i.e where is solr.xml
Step-2 edit the solr.in.sh file adding the
SOLR_AUTHENTICATION_CLIENT_CONFIGURER="org.apache.solr.client.solrj.impl.PreemptiveBasicAuthConfigurer"
SOLR_AUTHENTICATION_OPTS="-Dbasicauth=solr:SolrRocks"

step-3 restart server
step-4 try to adding the user using the htpp call
curl --user solr:SolrRocks http://localhost:8983/solr/admin/authentication -H 'Content-type:application/json' -d '{
"set-user": {"tom" : "TomIsCool" ,
"harry":"HarrysSecret"}}'
i am getting back error like

{
"responseHeader":

{ "status":400, "QTime":7}

,
"error":{
"metadata":[
"error-class","org.apache.solr.common.SolrException",
"root-error-class","org.apache.solr.common.SolrException"],
"msg":"No authentication plugin configured",
"code":400}}
please help me how resolve this