[REEF-885] Add apidoc_net to folders not deleted during website publish

JIRA:
  [REEF-885](https://issues.apache.org/jira/browse/REEF-885)

Pull request:
  This closes #1238
diff --git a/website/pom.xml b/website/pom.xml
index 60dec5a..e893c4b 100644
--- a/website/pom.xml
+++ b/website/pom.xml
@@ -85,6 +85,7 @@
                     <pubScmUrl>scm:svn:https://svn.apache.org/repos/asf/reef/</pubScmUrl>
                     <ignorePathsToDelete>
                         <ignorePathToDelete>apidocs/**</ignorePathToDelete>
+                        <ignorePathToDelete>apidoc_net/**</ignorePathToDelete>
                     </ignorePathsToDelete>
                 </configuration>
             </plugin>