Update git submodules

Update git submodules

* Update docs/submodules/barometer from branch 'master'
  - src: COLLECTD_CEILOMETER_* -> COLLECTD_OPENSTACK_*

    Since Ceilometer support was removed from the
    collectd-ceilometer-plugin[1] so references to
    collectd-ceilometer-plugin are misleading.

    This change updates variables COLLECTD_CEILOMETER_* ->
    COLLECTD_OPENSTACK_*

    [1] https://review.openstack.org/#/c/490823/

    This is an "internal" change, independant of repo rename

    Change-Id: I1247b59070fcb1eb378d9c702ddf9df0c26da878
    Signed-off-by: Emma Foley <emma.l.foley@intel.com>