Parametrize headless option for VirtualBox

If you need to start VirtualBox VMs without a GUI, for example, on a
remote computer, you can now set the 'headless' parameter in config.sh
to '1'.

DocImpact
Closes-Bug: #1304345

Change-Id: I868fa67335506a5e048d37411f5d5795b560a338
create_separate_images.sh: don't hard-code Ubuntu version

Change-Id: I7c748f111bbb45834868016d6c8f69f6af6e2d45
Fix uninstalled packages for ubuntu

1) bdsmainutils
Fixes heat deployment issues since puppet recipes improperly handle
`hexdump` presence.

Closes-Bug: #1389279

2) bridge-utils
Fixes the absence of `brctl` utility

Change-Id: Idbc1ec089723dfa01d0b91bfc0e2c9771d7805e7
Add neutronclient to fuel-ostf requirements

Neutronclient is required for new sanity and smoke scenarios for neutron

Change-Id: I86bc2511e2b1ba76645871ed59835441536d22d7
Related-blueprint: ostf-checks-for-neutron
Merge "create_separate_images.sh: don't hard-code Ubuntu version"
Merge "Parametrize headless option for VirtualBox"
Merge "Fix uninstalled packages for ubuntu"
Fix ubuntu diff repository structure

Change-Id: I2e4a37dd87769af10a3cf2a4dfeff01c0f1bafcb
Merge "Fix ubuntu diff repository structure"
Merge "Add neutronclient to fuel-ostf requirements"