Update git submodules

* Update docs/submodules/availability from branch 'master'
  - Sorting out git conflicts.

    ------------------------
    Updating based on March 29 OPNFV HA Meeting.
    Had general consensus on Heartbeating/Health-checking section and
    the VM Messaging section as a "PROPOSAL".

    I re-worded Title, Doc Status, Introduction and Conclusion to
    position the document as PROPOSAL status.

    ( NOTE I removed the more controversial VM Notification and
      Feedback section as we could not get to consensus on this
      topic in timeframe. )

    --------------------------
    Updating Commit based on online comments.
    Mostly clarifications of information already discussed.
    AND
    added HTML and PDF version of document for easier reading.

    --------------------------
    Updating Commit based on third round of review during OPNFV HA meetings,
    as well as submitted comments on the review.

    I updated the Overview document mostly with
       - specific deliverables for each capability
       - an indication in both the Introduction and the Conclusion that
         the intent or next steps for this proposal will be to review
         this document with the related teams of OPNFV (e.g. Doctor,
         Management & Orchestration) and OpenStack (Nova).

    I also removed the lower level documents from the commit
    since we need to focus on closing the high-level proposal first,
    and we haven't reviewed the lower level documents.

    --------------------------
    Updating Commit based on second round of review during OPNFV HA meetings,
    as well as submitted comments on the review.

    NOTE - I have ONLY updated the Overview document, looking to gain
    consensus on that before fixing up the lower level documents.

    The major update was to include the higher level context of how the
    proposed functionality integrates into the overall NFV / OpenStack
    architecture.  I have included such an Architecture Diagram for each
    of the major functionalities described in the document and updated
    the descriptions to describe this overall integration.

    --------------------------
    Updating Commit based on initial review during OPNFV HA meeting, as well
    as submitted comments on the review.

    Major updates included:
    - provided a new OVERVIEW document that describes the full suite of
      HA Guest APIs and focuses on how these APIs can be used to improve
      the availability of the hosted guest.
    - split the original document into two documents
        * Base Host-to-Guest Messaging Layer
             (that is leveraged by several HA Guest APIs)
        * Server Group Messaging API, OpenStack Host Design and Reference Guest Design
             (the first HA Guest API being considered for D release)

    --------------------------
    Committing draft version of HA Guest APIs - Server Group Messaging documentation
    for review.
    Word, PDF and rst versions of documentation are available.

    Change-Id: I1e44efe6052dfa84cdffd9bbebe8be86e4992121
    Signed-off-by: gwaines <greg.waines@windriver.com>

diff --git a/docs/submodules/availability b/docs/submodules/availability
index 126074a..54961e9 160000 (submodule)
--- a/docs/submodules/availability
+++ b/docs/submodules/availability
@@ -1 +1 @@
-Subproject commit 126074a0899cd51afda5da62a6db8d3bed030199
+Subproject commit 54961e9deb343b3d45d0ae0295729af207ec8451