Fix docker assembly by ensuring the directory is clean first. (#117)

* Fix docker assembly by ensuring the directory is clean first.

* Hack new version of clean plugin since parent pom upgrade not possible at this time.

Author: vjkoskela

pom.xml

@@ -263,6 +263,32 @@
         <inherited>false</inherited>
       </plugin>
       <!-- Project Specific Plugins -->
+      <plugin>
+        <artifactId>maven-clean-plugin</artifactId>
+        <!-- TODO(ville): Cannot upgrade parent pom to latest without some major
+             cleanup in this project (which is underway separately) but fixing
+             the docker build in the short-term is more important. -->
+       <!--<version>${maven.clean.plugin.version}</version>-->
+        <version>3.1.0</version>
+        <executions>
+          <execution>
+            <id>clean-assemblies</id>
+            <phase>initialize</phase>
+            <goals>
+              <goal>clean</goal>
+            </goals>
+            <configuration>
+             <excludeDefaultDirectories>true</excludeDefaultDirectories>
+             <verbose>true</verbose>
+             <filesets>
+                <fileset>
+                  <directory>${project.build.directory}/docker-assembly</directory>
+                </fileset>
+              </filesets>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
       <plugin>
         <groupId>org.codehaus.mojo</groupId>
         <artifactId>appassembler-maven-plugin</artifactId>