fix file link in plugins

Running builds leave a file link with an error like "http://gitlab.example.com/root/project/blob/master/index.php#L6" but it is pointing to the actual file, not the file with a bug, example "97f0a6453d/index.php (L6)"

Close #915

PHPCI/Model/Build/GitlabBuild.php

@@ -47,7 +47,7 @@ class GitlabBuild extends RemoteGitBuild
             'http://%s/%s/blob/%s/{FILE}#L{LINE}',
             $this->getProject()->getAccessInformation("domain"),
             $this->getProject()->getReference(),
-            $this->getBranch()
+            $this->getCommitId()
         );
     }