Update git submodules

Update git submodules

* Update docs/submodules/functest from branch 'stable/fraser'
  - Update juju agents

    It conforms with last juju update.

    Change-Id: I4941aac66e5ac96045090f10f197f6ee2712caac
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>
    (cherry picked from commit 1ab7a53dab08a6f67ff2cf54f33b70dea0e82bfb)

  - Update Juju to 2.3.9

    It should fix the key bug about subnet discovery.
    Now juju_epc may run in parallel of rally testcases.

    Change-Id: I04c1fcf2a18b461e5809d436846aa52c4b2660c8
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>
    (cherry picked from commit a51d42200d94643314ece1a833181a7193ce2265)