Add some @Conditionals to enable non-netflix apps to start

spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/eureka/EurekaClientAutoConfiguration.java

@@ -41,6 +41,7 @@ import com.netflix.discovery.converters.XmlXStream;
 @Configuration
 @EnableConfigurationProperties
 @ConditionalOnClass(EurekaClientConfig.class)
+@ConditionalOnBean(DiscoveryClient.class)
 @ConditionalOnExpression("${eureka.client.enabled:true}")
 public class EurekaClientAutoConfiguration {
 

spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/ribbon/RibbonAutoConfiguration.java

@@ -6,6 +6,7 @@ import java.util.List;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.autoconfigure.AutoConfigureAfter;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;
 import org.springframework.cloud.netflix.eureka.EurekaClientAutoConfiguration;
@@ -22,6 +23,7 @@ import com.netflix.loadbalancer.BaseLoadBalancer;
  * @author Dave Syer
  */
 @Configuration
+@ConditionalOnBean(SpringClientFactory.class)
 @AutoConfigureAfter(EurekaClientAutoConfiguration.class)
 public class RibbonAutoConfiguration {