Why unable to access the rhevm service after a 'yum update' on the rhevm server ?

Issue

• After running "yum update" on RHEV-M server, GUI fails to come up with below error.

HTTP Error 404: Not Found

• Jboss server.log shows below error.

java.lang.ClassNotFoundException: org.hsqldb.jdbcDriver from BaseClassLoader@6e26d149{vfsfile:/var/lib/jbossas/server/rhevm-slimmed/deploy/hsqldb-ds.xml}