Update git submodules

Update git submodules

* Update docs/submodules/functest from branch 'stable/danube'
  - Disable tempest server reboot test for SDNVPN and Gluon

    Bug report: https://bugs.opendaylight.org/show_bug.cgi?id=5586
    As a result, floating IPs are not working in Apex at the moment.

    Change-Id: I437c10b53dc01810ed757f040d3378c92320274b
    Signed-off-by: Georg Kunz <georg.kunz@ericsson.com>
    Signed-off-by: Nikolas Hermanns <nikolas.hermanns@ericsson.com>
    (cherry picked from commit 9fba4aed6b8f2ef1c939498d866f2cae57b89246)