Update git submodules

* Update docs/submodules/barometer from branch 'master'
  - ci: update collectd version

    Upadtes the version of collectd that is built nightly.
    Collectd version reflects master on July 19th, 2017

    Change-Id: I15ffd50eaa9fc92d0636f2866705736ce64e497b
    Signed-off-by: Emma Foley <emma.l.foley@intel.com>

diff --git a/docs/submodules/barometer b/docs/submodules/barometer
index 6c0c441..24b8f02 160000 (submodule)
--- a/docs/submodules/barometer
+++ b/docs/submodules/barometer
@@ -1 +1 @@
-Subproject commit 6c0c441e0678ade77c5242f83520f2dc3b5ddef1
+Subproject commit 24b8f02a1c9c6a59f4c53a0b7a4ea6d0978ee391