Update git submodules

Update git submodules

* Update docs/submodules/so.git from branch 'master'
  to 20a24c8e780890d4e63b281e5de16080d322bf17
  - Merge "Create Pre Building Block validator"
  - Create Pre Building Block validator

    Use Flowvalidator shouldRunFor method to check if flow needs to be
    validated.
    Create Pre Building Block validator to check if cloud-region
    orchestration-disabled is true

    Change-Id: I2f1dca16c97505292d9b99f7e206713e4963261f
    Issue-ID: SO-1534
    Signed-off-by: Benjamin, Max (mb388a) <mb388a@us.att.com>