Update git submodules

Update git submodules

* Update docs/submodules/functest from branch 'master'
  - Call fetch_os_creds.sh from $PATH

    Now it's defined as script in releng/modules' setup.py [1]

    [1] https://gerrit.opnfv.org/gerrit/#/c/35183/

    Co-Authored-By: Cédric Ollivier <cedric.ollivier@orange.com>
    Depends-On: Ic77f4e46d6d3396f9891b73105a0eb7aa037754f
    JIRA: FUNCTEST-829

    Change-Id: Ief821b7326e0a6c2bbcab31bb21629455e4bc9ea
    Signed-off-by: Linda Wang <wangwulin@huawei.com>
    Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>