docker: create a mount point for IBP image build directory
docker: create a mount point for IBP image build directory

Makes IBP images build time reasonable, especially if the master
node runs in a VM.

fuel_agent (which builds Ubuntu images) runs in the mcollective
container. In general OS setup generates quite a lot of IO.
fuel_agent builds the OS image in a loopback filesystem, which
results in an extra overhead. A container filesystem is backed
by dm-snapshot which is known to have a poor write performance,
especially for large files (like OS images). By default docker
storage is a loopback file residing in /var/lib/docker. Thus
the data written to the OS image being built goes through a number
of layers:

ext4 -> loop -> dm-snapshot (/var/lib/docker-> loop ->
     -> ext4 (/var/lib/docker) -> dm-linear (os-varlibdocker) ->
     -> hard drive

If the master node runs on a VM rather than a physcial hardware
the above chain gets even more complicated:

ext4 -> loop -> dm-snapshot (/var/lib/docker-> loop ->
     -> ext4 (/var/lib/docker) -> dm-linear (os-varlibdocker) ->
     -> virtual hard drive (qemu) -> qcow2 -> ext4 (host)

The write performance of such a setup is awful, as a result making
the basic Ubuntu installation takes more than 15 minutes.

Using the volume makes it possible to eliminate the extra layers,
so the written data goes through

ext4 -> loop -> ext4 -> dm-linear (os-var) -> hard drive

Related-Bug: #1457643
Change-Id: Ie47be6227e48049bc1dd3bb46fb1e58fd06d194f

eayunstack/fuel-main,huntxu/fuel-main,teselkin/fuel-main,AnselZhangGit/fuel-main,teselkin/fuel-main,AnselZhangGit/fuel-main,huntxu/fuel-main,eayunstack/fuel-main,AnselZhangGit/fuel-main,SmartInfrastructures/fuel-main-dev,SergK/fuel-main,AnselZhangGit/fuel-main,stackforge/fuel-main,stackforge/fuel-main,teselkin/fuel-main,stackforge/fuel-main,huntxu/fuel-main,SmartInfrastructures/fuel-main-dev,eayunstack/fuel-main,SmartInfrastructures/fuel-main-dev,teselkin/fuel-main,SergK/fuel-main,SergK/fuel-main,SmartInfrastructures/fuel-main-dev