[FIXED JENKINS-4959] Add Downstream blocking for matrix projects.

changelog.html

@@ -67,6 +67,9 @@ Upcoming changes</a>
   <li class=bug>
     Fixed the permission issues on /Applications/Jenkins with OS X installer
     (<a href="https://issues.jenkins-ci.org/browse/JENKINS-9398">issue 9398</a>)
+  <li class=bug>
+    Block up-/downstream Projects of matrix projects
+    (<a href="https://issues.jenkins-ci.org/browse/JENKINS-4959">issue 4959</a>)
   <li class=rfe>
     Just like SSH connector, managed Windows connector now allows the machine name to be specified.
     (<a href="https://github.com/jenkinsci/jenkins/pull/172">pull request #172</a>)

core/src/main/resources/hudson/matrix/MatrixProject/configure-entries.jelly

@@ -35,6 +35,7 @@ THE SOFTWARE.
       <p:config-quietPeriod />
       <p:config-retryCount />
       <p:config-blockWhenUpstreamBuilding />
+      <p:config-blockWhenDownstreamBuilding />
       <p:config-customWorkspace />
     </f:advanced>
   </f:section>