Update git submodules

* Update docs/submodules/barometer from branch 'master'
  - Clean up barometer-collectd Dockerfile

    By merging several of the RUN lines and executing a yum cleanup all
    at the end of the dependency installation, the resulting container
    image will be around 300MB smaller.

    Change-Id: I63139a5283ea40ec8ea5cc3fd7aa7faddc90f3ce
    Signed-off-by: Leif Madsen <lmadsen@redhat.com>

diff --git a/docs/submodules/barometer b/docs/submodules/barometer
index 63b5557..307db2d 160000 (submodule)
--- a/docs/submodules/barometer
+++ b/docs/submodules/barometer
@@ -1 +1 @@
-Subproject commit 63b55576a2290a1a9d6bb48dc72667967bbd8920
+Subproject commit 307db2dfb4050619601f9e02375d4c64e5525c43