xenapi: enable user interaction with stack.sh

In XenServer, devstack runs inside a virtual machine. This makes it hard
for the user to interact with stack.sh should a parameter be missing.
This change will create an upstart job (devstack) that runs
stack.sh with console enabled so user can interact with it by running
vncviewer or using XenCenter.

Logging the output is also disabled, stamp files are used instead to
detect the script run status in case install_os_domU.sh is used.

As run.sh.log is removed, standard devstack logging should be used.

The change also removes the environment settings from run.sh, as they
are not needed, they should be specified in localrc. This way user
cannot get different experiences by using unstack.sh/stack.sh or run.sh

Also a proper unstack.sh is called instead of killing screen in run.sh

Change-Id: I7eb12bd74746cc7a1db3aa9fd68ece645a50001d
Fix noVNC git repo

Recent change switched base git URL to git.openstack.org.
However, noVNC is only hosted on GitHub.
Change git repo URL for noVNC back to the GitHub one.

Change-Id: Iaa9f570639301be1c29cc400c1c73afcbf637b70
Merge "Fix noVNC git repo"
Merge "xenapi: enable user interaction with stack.sh"
Merge branch 'master' of github.com:openstack-dev/devstack