Mova nova configuration initialization

* Move shared volume configuration from stack.sh to stackrc
* Move Nova network and vnc/spice configuration settings from stack.sh
  into lib/nova
* Rename NET_MAN to NETOWRK_MANAGER to match nova.conf attribute name

Change-Id: I9bd2955def553499aa832eda1f0959afe494206a
Fix typo in baremetal header comment.

Change-Id: I553c37581c92dcdc13e0d8dcdb9c8be7309deaa1
Force Quantum processes to run in a subshell

Force bash to evaluate the command line passed to screen_it so the
commands are executed in a subshell.  This seems to make a difference
when using run_service() when the server process is owned by init.

These Quantum services were the only ones in all of DevStack being
spawned in this manner.  This will allow the run_service() patch
https://review.openstack.org/#/c/23148/ to succesfully be merged
and the number of test failures due to screen should be reduced to 0.

Change-Id: I97d562adda51d39a5e7fa1dc4d945d4a396201cd
Enable multi-agent support

even when q-svc is disabled, i.e. on node without q-svc in multi-agent architecture,
state_path will be configured in quantum.conf so that agent doesn't crashs anymore

Bug 1156685

Change-Id: I28625e4b606fa61c35179248321632d3d797c547
Merge "Force Quantum processes to run in a subshell"
Add run_process() to start services without screen

* USE_SCREEN defaults to True, set it to False to exec the services
  directly via bash.  SCREEN_DEV is still supported until the CI
  scripts get updated.
* The extra logging file descriptors are properly closed in the child process
  and stdout/stderr are redirected to the log files.
* The screen_rc() call is still present; this means that stack-screenrc will
  have a complete record of what was started and rejoin-stack.sh may be able
  to re-create the setup under screen.
* The python interpreter was unwilling to write to the log files without
  unbufering stdout by using PYTHONUNBUFFERED.  This feels hackish and should
  be investigated further.

Change-Id: I012ed049f2c8b185a2e6929d73edc29e167bc21f
Merge "Enable multi-agent support"
Merge "Add run_process() to start services without screen"
Merge "Mova nova configuration initialization"