GUAC-1170: Add missing Maven plugin versions.

guacamole-common/pom.xml

@@ -70,6 +70,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-source-plugin</artifactId>
+                <version>2.4</version>
                 <executions>
                     <execution>
                         <id>attach-sources</id>
@@ -84,6 +85,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-javadoc-plugin</artifactId>
+                <version>2.10.3</version>
                 <configuration>
                     <detectOfflineLinks>false</detectOfflineLinks>
                 </configuration>