elasticsearch 7.17.3 uses JDK >= 18 which changed the value of
"java.security.manager" property to "disallow".
As a consequence a "java.lang.UnsupportedOperationException" is
now raised when bootstrapping elasticsearch server used in tests.
So explicitely set the "java.security.manager" property to "allow"
to avoid that exception raising when elasticsearch setups its custom
security manager.