As an option you can start the HBase REST server manually after the install process is complete. It can be started on any host that has the HBase Master or the Region Server installed.
If you attempt to start the HBase REST server on the same host as the Ambari server, however, you need to start it with the -p option, as its default port is 8080 and that conflicts with the Ambari Web default port. Use the following command to start the REST server.
/usr/lib/hbase/bin/hbase-daemon.sh start rest -p <custom_port_number>