Missing plugin version

(cherry-pick from master branch)

Yang plugin had missing version causing build failure.
For some reason, it just now became an issue.

Change-Id: If9651a9cdc5f568cd2361fc0e1e80088843b1292
Signed-off-by: Patrick Brady <pb071s@att.com>
Issue-ID: APPC-324
diff --git a/appc-oam/appc-oam-bundle/pom.xml b/appc-oam/appc-oam-bundle/pom.xml
index 7954011..9d3014f 100644
--- a/appc-oam/appc-oam-bundle/pom.xml
+++ b/appc-oam/appc-oam-bundle/pom.xml
@@ -42,6 +42,7 @@
             <plugin>
                 <groupId>org.opendaylight.yangtools</groupId>
                 <artifactId>yang-maven-plugin</artifactId>
+                <version>${odl.yangtools.version}</version>
                 <executions>
                     <execution>
                         <id>config</id>