Support Spring Boot 2.0.0.RELEASE and Spring Cloud 2.0.0

[qiyi]

The current spring-cloud-etcd version with Spring boot 2.0.0.Release and Spring cloud 2.0.0.M8 will start fail with these exceptions:

Caused by: java.lang.IllegalStateException: Failed to introspect annotated methods on class org.springframework.cloud.etcd.EtcdAutoConfiguration
        at org.springframework.core.type.StandardAnnotationMetadata.getAnnotatedMethods(StandardAnnotationMetadata.java:169) ~[spring-core-5.0.4.RELEASE.jar:5.0.4.RELEASE]
        at org.springframework.context.annotation.ConfigurationClassParser.retrieveBeanMethodMetadata(ConfigurationClassParser.java:386) ~[spring-context-5.0.4.RELEASE.jar:5.0.4.RELEASE]
        at org.springframework.context.annotation.ConfigurationClassParser.doProcessConfigurationClass(ConfigurationClassParser.java:311) ~[spring-context-5.0.4.RELEASE.jar:5.0.4.RELEASE]
        at org.springframework.context.annotation.ConfigurationClassParser.processConfigurationClass(ConfigurationClassParser.java:241) ~[spring-context-5.0.4.RELEASE.jar:5.0.4.RELEASE]
        at org.springframework.context.annotation.ConfigurationClassParser.processImports(ConfigurationClassParser.java:606) ~[spring-context-5.0.4.RELEASE.jar:5.0.4.RELEASE]
        ... 94 common frames omitted
Caused by: java.lang.NoClassDefFoundError: org/springframework/boot/actuate/endpoint/AbstractEndpoint
        at java.lang.ClassLoader.defineClass1(Native Method) ~[na:1.8.0_152]
        at java.lang.ClassLoader.defineClass(ClassLoader.java:763) ~[na:1.8.0_152]
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142) ~[na:1.8.0_152]
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:467) ~[na:1.8.0_152]
        at java.net.URLClassLoader.access$100(URLClassLoader.java:73) ~[na:1.8.0_152]
        at java.net.URLClassLoader$1.run(URLClassLoader.java:368) ~[na:1.8.0_152]
        at java.net.URLClassLoader$1.run(URLClassLoader.java:362) ~[na:1.8.0_152]
        at java.security.AccessController.doPrivileged(Native Method) ~[na:1.8.0_152]
        at java.net.URLClassLoader.findClass(URLClassLoader.java:361) ~[na:1.8.0_152]
        at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[na:1.8.0_152]
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:338) ~[na:1.8.0_152]
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[na:1.8.0_152]
        at java.lang.Class.getDeclaredMethods0(Native Method) ~[na:1.8.0_152]
        at java.lang.Class.privateGetDeclaredMethods(Class.java:2701) ~[na:1.8.0_152]
        at java.lang.Class.getDeclaredMethods(Class.java:1975) ~[na:1.8.0_152]
        at org.springframework.core.type.StandardAnnotationMetadata.getAnnotatedMethods(StandardAnnotationMetadata.java:158) ~[spring-core-5.0.4.RELEASE.jar:5.0.4.RELEASE]

because of the inherited class org/springframework/boot/actuate/endpoint/AbstractEndpoint was removed.