Update git submodules

Update git submodules

* Update docs/submodules/releng-xci from branch 'master'
  - Merge "xci: scripts: vm: Update package manager cache and ignore errors"
  - xci: scripts: vm: Update package manager cache and ignore errors

    We need to make sure that the local package cache is updated before we
    try to install packages. Moreover, from time to time, something in the
    repos may be broken so we don't want to break the CI job. As such, make
    that step non-fatal as simply send the output to stdout so we can see
    what's wrong.

    Change-Id: I148e3b5435c604bb0d54339935255740c8ce07c0
    Signed-off-by: Markos Chandras <mchandras@suse.de>