Update git submodules

Update git submodules

* Update docs/submodules/fuel from branch 'stable/euphrates'
  - Merge "deploy.sh: Check hypervisor after prereq install" into stable/euphrates
  - deploy.sh: Check hypervisor after prereq install

    On a clean system (i.e. no libvirt installed), the prerequisites
    should be installed first, before checking for hypervisor access.

    While at it, add 'libvirt' to the list of prerequisites, as it is
    not automatically required by the others.

    Add a note in the documentation about libvirtd service not being
    automatically started after installation on CentOS.

    Change-Id: I29d94d4a56cd823362811e8fc9c076c83fb6c04c
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>
    (cherry picked from commit 8bdc7b442ebd9f162a36f568d9b61ecf85ab23cb)