Set DB_CLOSE_ON_EXIT=false in H2EmbeddedDbConfig

This commit sets the DB_CLOSE_ON_EXIT flag to false for embedded H2
databases loaded using H2EmbeddedDatabaseConfigurer (i.e., via Spring's
<jdbc:embedded-database /> XML namespace, EmbeddedDatabaseBuilder,
EmbeddedDatabaseFactory, and EmbeddedDatabaseFactoryBean).

Issue: SPR-11573