Update git submodules

Update git submodules

* Update docs/submodules/aai/aai-common.git from branch 'master'
  to 31b7af4804219e5f03faeecef55f041f48adb6d5
  - Fix a potential bug in DBSerializer

    where the assumption is the aai-node-type property will
    exist on the node types. There is a case where a vertex
    is in the process of being deleted and during that time
    the vertex will be missing some properties and during
    that time the GET with depth all will result in exception
    This is possible because of our database being
    an eventually consistent database

    Issue-ID: AAI-2330
    Change-Id: I2b11c9a2ec5c3b6bffd2690a0c075962e80781cc
    Signed-off-by: Kajur, Harish (vk250x) <vk250x@att.com>