When externalizing the PostgresSQL Database, Red Hat Single Sign-On (RH SSO) deployed in OpenShift Container Platform (OCP) returns the error "Unable to create connection"

Issue

After attempting to externalize the PostgreSQL Database, the RH SSO pod doesn't start and following error is shown in the logs:

[0m[33m11:14:02,769 WARN  [org.jboss.jca.core.connectionmanager.pool.strategy.OnePool] (MSC service thread 1-1) IJ000604: Throwable while attempting to get a new connection: null: javax.resource.ResourceException: IJ031084: Unable to create connection
    at org.jboss.ironjacamar.jdbcadapters@1.4.30.Final-redhat-00001//org.jboss.jca.adapters.jdbc.local.LocalManagedConnectionFactory.createLocalManagedConnection(LocalManagedConnectionFactory.java:364)
    at org.jboss.ironjacamar.jdbcadapters@1.4.30.Final-redhat-00001//org.jboss.jca.adapters.jdbc.local.LocalManagedConnectionFactory.getLocalManagedConnection(LocalManagedConnectionFactory.java:371)
    at org.jboss.ironjacamar.jdbcadapters@1.4.30.Final-redhat-00001//org.jboss.jca.adapters.jdbc.local.LocalManagedConnectionFactory.createManagedConnection(LocalManagedConnectionFactory.java:287)
    at org.jboss.ironjacamar.impl@1.4.30.Final-redhat-00001//org.jboss.jca.core.connectionmanager.pool.mcp.SemaphoreConcurrentLinkedDequeManagedConnectionPool.createConnectionEventListener(SemaphoreConcurrentLinkedDequeManagedConnectionPool.java:1322)