Impacted versions:
9.0 Community & 9.0 Enterprise

Steps to reproduce:
- Open up a V9 runbot
- Go to projects and click on the issues item, for example for the project 'Research & Development':
  ![image](https://cloud.githubusercontent.com/assets/6352350/13873686/65f2c31c-ecf3-11e5-917a-38df2832bd00.png)
- The project tasks view is opened in place of the project issues. (notice that this only happens every once in a while, about once in five attempts) Example:
  ![image](https://cloud.githubusercontent.com/assets/6352350/13873789/14798b64-ecf4-11e5-9b77-f2ad5d3a8adc.png)

Current behavior:
Every once in a while (about one out of five attempts) after clicking on the issues button it will open up the project tasks, not the issues.

Expected behavior:
When you click on the issues the view with all issues opens, not the view for all tasks.

addons/project_issue/project_issue.py
Parameter of the stage search taken from the issue:
            - type: stage type must be the same or 'both'
            - team_id: if set, stages must belong to this team or
              be a default case
        """
        if isinstance(cases, (int, long)):
            cases = self.browse(cr, uid, cases, context=context)
        # co
        team_ids = []
        if team_id:
            team_ids.append(team_id)
        for task in cases:
            if task.project_id:
                team_ids.append(task.project_id.id)
        # OR 
        search_domain = []
        if team_ids:
            search_domain += [('|')] * (len(team_ids)-1)
            for team_id in team_ids:
                search_domain.append(('project_ids', '=', team_id))
        search_domain += list(domain)
        # pe
        stage_ids = self.pool.get('project.task.type').search(cr, uid, search_domain, order=order, context=context)
        if stage_ids:
            return stage_ids[0]
        return False
    # --
    # Ma
    # --
    def _track_subtype(self, cr, uid, ids, init_values, context=None):