Stop relying on Artemis's on-demand queue creation in CLI JMS test

Artemis's on-demand queue cretaion appears to be rather flakey,
sometimes failing with a NullPointerException.

This commit ensures that the queue used by the sample is created
during start up rather than on demand. This will hopefully make the
test that runs the sample more robust.

Closes gh-7346

spring-boot-cli/src/test/java/org/springframework/boot/cli/SampleIntegrationTests.java

@@ -144,8 +144,15 @@ public class SampleIntegrationTests {
 
 	@Test
 	public void jmsSample() throws Exception {
-		String output = this.cli.run("jms.groovy");
-		assertThat(output).contains("Received Greetings from Spring Boot via Artemis");
+		System.setProperty("spring.artemis.embedded.queues", "spring-boot");
+		try {
+			String output = this.cli.run("jms.groovy");
+			assertThat(output)
+					.contains("Received Greetings from Spring Boot via Artemis");
+		}
+		finally {
+			System.clearProperty("spring.artemis.embedded.queues");
+		}
 	}
 
 	@Test