Improve cache sample

Clarify the cache sample and in particular that Infinispan does not
bootstrap with a default configuration file. Hence the custom
`infinispan.xml` configuration is enabled by default if Infinispan is
available on the classpath.

See gh-9417

spring-boot-samples/spring-boot-sample-cache/README.adoc

@@ -85,9 +85,8 @@ TIP: Run sample cache application using Hazelcast with
 === Infinispan
 Add the `org.infinispan:infinispan-spring4-embedded` dependency to enable support for
 Infinispan. There is no default location that Infinispan uses to look for a config
-file so if you don't specify anything it will bootstrap on a hardcoded default. You
-can set the `spring.cache.infinispan.config` property to use the provided
-`infinispan.xml` configuration instead.
+file so this sample is configured to use a the provider `infinispan.xml` configuration
+file specified via the `spring.cache.infinispan.config` property.
 
 TIP: Run sample cache application using Infinispan with
 `$mvn spring-boot:run -Pinfinispan`.

spring-boot-samples/spring-boot-sample-cache/src/main/resources/application.properties

@@ -3,7 +3,7 @@ management.security.enabled=false
 #
 # Infinispan configuration file location.
 #
-#spring.cache.infinispan.config=infinispan.xml
+spring.cache.infinispan.config=infinispan.xml
 
 
 #
@@ -15,10 +15,10 @@ management.security.enabled=false
 #
 # Caffeine configuration
 #
-#spring.cache.caffeine.spec=maximumSize=200,expireAfterAccess=600s
+spring.cache.caffeine.spec=maximumSize=200,expireAfterAccess=600s
 
 
 #
 # Guava configuration
 #
-#spring.cache.guava.spec=maximumSize=200,expireAfterAccess=600s
+spring.cache.guava.spec=maximumSize=200,expireAfterAccess=600s

spring-boot-samples/spring-boot-sample-cache/src/main/resources/infinispan.xml

 <?xml version="1.0" encoding="UTF-8"?>
-<infinispan xmlns="urn:infinispan:config:7.2">
+<infinispan xmlns="urn:infinispan:config:8.2">
 
 	<cache-container default-cache="default">
-		<local-cache name="countries" statistics="true">
+		<local-cache name="default"/>
+		<local-cache name="countries">
 			<eviction max-entries="200"/>
 			<expiration lifespan="600000"/>
 		</local-cache>