Workaround steps

Step1 : Create 'extensions' folder(in current directory from where you are executing the oc command)
~~~
mkdir -p extensions
~~~

Step2 : Create postconfigure.sh script(see the 'cat' command) with the below quoteed contents in 'extensions' folder

$ cat extensions/postconfigure.sh 
~~~~~~
#!/bin/sh
echo "Executing postconfigure.sh"
$JBOSS_HOME/bin/jboss-cli.sh --file=$JBOSS_HOME/extensions/extensions.cli
~~~~~~

Step3: Create 'extensions.cli' with below contents in 'extensions' folder  

NOTE:  Please change change the connection-url(database type, host , port, database name or schema name), user-name, password entries from the following data-source script.

$ cat extensions/extensions.cli 
~~~~~~
embed-server --std-out=echo --server-config=standalone-openshift.xml
batch
data-source add --name=KeycloakDS --jndi-name=java:jboss/datasources/KeycloakDS --driver-name=postgresql --connection-url=jdbc:postgresql://localhost:5432/rhsso71 --user-name=postgres --password=test123 --validate-on-match=true --background-validation=false --valid-connection-checker-class-name=org.jboss.jca.adapters.jdbc.extensions.postgres.PostgreSQLValidConnectionChecker --exception-sorter-class-name=org.jboss.jca.adapters.jdbc.extensions.postgres.PostgreSQLExceptionSorter
run-batch
quit
~~~~~~~


Step4 : Create 'configmap' from above created scripts ('postconfigure.sh', 'extensions.cli')

~~~~~~~
$ oc create configmap jboss-cli --from-file=postconfigure.sh=extensions/postconfigure.sh --from-file=extensions.cli=extensions/extensions.cli
~~~~~~~

Step5 : Create volume for the above created 'confimap'. 
NOTE: change the <dc-name> with deployment-config name of kie server
~~~~~
$ oc set volume dc/<dc-name> --add --name=jboss-cli -m /opt/eap/extensions -t configmap --configmap-name=jboss-cli --default-mode='0755'