Attempt to fix server test CI failures

Switch surefire configuration so that forking isn't used. This seems to
prevent the "Corrupted STDOUT by directly writing to native stream"
errors and will hopefully reduce failures on the CI server.

See gh-12689

spring-boot-tests/spring-boot-integration-tests/spring-boot-server-tests/pom.xml

@@ -56,6 +56,9 @@
 						<maven.home>${maven.home}</maven.home>
 						<repository>${repository}</repository>
 					</systemPropertyVariables>
+					<useSystemClassLoader>false</useSystemClassLoader>
+					<forkCount>0</forkCount>
+					<reuseForks>false</reuseForks>
 				</configuration>
 			</plugin>
 		</plugins>