sample: upgrade dubbo to 2.7.1
diff --git a/samples/dubbo-sample-service/pom.xml b/samples/dubbo-sample-service/pom.xml
index 2ad87e0..7c09fdb 100644
--- a/samples/dubbo-sample-service/pom.xml
+++ b/samples/dubbo-sample-service/pom.xml
@@ -30,14 +30,9 @@
             <version>1.1.1</version>
         </dependency>
         <dependency>
-            <groupId>com.alibaba</groupId>
+            <groupId>org.apache.dubbo</groupId>
             <artifactId>dubbo</artifactId>
-            <version>2.5.3</version>
-        </dependency>
-        <dependency>
-            <groupId>org.javassist</groupId>
-            <artifactId>javassist</artifactId>
-            <version>3.18.1-GA</version>
+            <version>2.7.1</version>
         </dependency>
         <dependency>
             <groupId>log4j</groupId>
@@ -63,30 +58,14 @@
             </exclusions>
         </dependency>
         <dependency>
-            <groupId>org.springframework</groupId>
-            <artifactId>spring</artifactId>
-            <version>2.5.6.SEC03</version>
-        </dependency>
-        <dependency>
-            <groupId>org.slf4j</groupId>
-            <artifactId>slf4j-api</artifactId>
-            <version>1.7.6</version>
-        </dependency>
-        <dependency>
-            <groupId>log4j</groupId>
-            <artifactId>log4j</artifactId>
-            <version>1.2.9</version>
-        </dependency>
-
-        <dependency>
             <groupId>org.slf4j</groupId>
             <artifactId>slf4j-log4j12</artifactId>
             <version>1.6.1</version>
         </dependency>
         <dependency>
-            <groupId>com.101tec</groupId>
-            <artifactId>zkclient</artifactId>
-            <version>0.4</version>
+            <groupId>org.apache.curator</groupId>
+            <artifactId>curator-recipes</artifactId>
+            <version>2.12.0</version>
         </dependency>
     </dependencies>