Update git submodules

Update git submodules

* Update docs/submodules/openretriever from branch 'master'
  - Merge "Clarifications to OpenStack gaps"
  - Clarifications to OpenStack gaps

    I've made the following changes:
      - removed the direct references to Mitaka release, as this analyzis
    might be updated to later releases.
      - Added the relevant OpenStack projects to the table
      - Made some clarifications to the existing gaps
      - Removed the "Is available in Mitaka" as none of them are avaiable ;)

    Change-Id: I48a4695de8e3d72b7fbcd2287d62b4b178758051
    Signed-off-by: csatari <gergely.csatari@nokia.com>