Provide original BootstrapContext to ConfigDataContextRefresher

RefreshBootstrapRegistryInitializer saves the BootstrapContext to the application context so ConfigDataContextRefresher can reuse it during rebind.

This fixes issues where custom beans were created such as RestTemplate or discovery first config server lookup.

Fixes gh-933

spring-cloud-context/src/test/java/org/springframework/cloud/context/refresh/ConfigDataContextRefresherIntegrationTests.java

@@ -27,6 +27,8 @@ import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
+import org.springframework.boot.BootstrapRegistry.InstanceSupplier;
+import org.springframework.boot.ConfigurableBootstrapContext;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.context.config.ConfigData;
@@ -129,6 +131,13 @@ public class ConfigDataContextRefresherIntegrationTests {
 		then(cachedRandomLong).isEqualTo(properties.cachedRandomLong);
 	}
 
+	@Test
+	public void contextContainsBootstrapContext() {
+		ConfigurableBootstrapContext bootstrapContext = context.getBean(ConfigurableBootstrapContext.class);
+		then(bootstrapContext).isNotNull();
+		then(bootstrapContext.isRegistered(MyTestBean.class)).isTrue();
+	}
+
 	protected static class TestEnvPostProcessor implements EnvironmentPostProcessor, Ordered {
 
 		@Override
@@ -189,6 +198,7 @@ public class ConfigDataContextRefresherIntegrationTests {
 		public List<TestConfigDataResource> resolve(ConfigDataLocationResolverContext context,
 				ConfigDataLocation location)
 				throws ConfigDataLocationNotFoundException, ConfigDataResourceNotFoundException {
+			context.getBootstrapContext().registerIfAbsent(MyTestBean.class, InstanceSupplier.of(new MyTestBean()));
 			return Collections.singletonList(new TestConfigDataResource(count.get()));
 		}
 
@@ -206,6 +216,10 @@ public class ConfigDataContextRefresherIntegrationTests {
 
 	}
 
+	protected static class MyTestBean {
+
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	@EnableConfigurationProperties(TestProperties.class)
 	@EnableAutoConfiguration