flume-checkstyle module should use ASF root pom as parent

The flume-checkstyle module doesn't currently declare a parent pom. This
will be a problem when we try to deploy our artifacts because we are
missing a distributionManagement section in the flume-checkstyle module.
The deploy will fail with an error message that looks something like:

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-deploy-plugin:2.7:deploy (default-deploy)
on project flume-checkstyle: Deployment failed: repository element was not specified in the POM inside
distributionManagement element or in -DaltDeploymentRepository=id::layout::url parameter

This patch should solve the problem.

Reviewers: Attila Simon, Denes Arvay, Bessenyei Balázs Donát

Closes apache#109.

flume-checkstyle/pom.xml

@@ -21,11 +21,18 @@
   xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
   <modelVersion>4.0.0</modelVersion>
 
+  <parent>
+    <groupId>org.apache</groupId>
+    <artifactId>apache</artifactId>
+    <version>18</version>
+  </parent>
+
   <groupId>org.apache.flume</groupId>
   <artifactId>flume-checkstyle</artifactId>
-  <name>Flume checkstyle project</name>
   <version>1.8.0-SNAPSHOT</version>
 
+  <name>Flume checkstyle project</name>
+
   <properties>
     <!-- Set default encoding to UTF-8 to remove maven complaints -->
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>