Update git submodules

Update git submodules

* Update docs/submodules/barometer from branch 'master'
  - Merge "src: rename dir - collectd-ceilometer-plugin/ -> collectd-openstack-plugin/"
  - src: rename dir - collectd-ceilometer-plugin/ -> collectd-openstack-plugin/

    Updating the directory to keep naming consistent
    with project rename [1] i.e. no specific mention of
    ceilometer.

    [1] https://review.openstack.org/#/c/500768/

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

    Change-Id: I6cf22c081aa1e40f64995be40b6225855faf4092
    Signed-off-by: Emma Foley <emma.l.foley@intel.com>