If xenstore is missing, keep retrying to connect rather than failing

Ultimately we should modify the upstream xenstore client to be able
to handle (re-)connection, allowing us to restart the xenstore service.
For now we work around xenstore being missing in this client only
because we want squeezed to work just well enough for xapi to start.

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
get_domain_zero_policy should run on bare-metal as well as xen

Rather than querying the VM's max_pages via xen, we ask Linux itself
via /proc/meminfo. This enables the function to work -- and xapi to
start -- even if we haven't (yet) booted into a xen system.

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Merge pull request #17 from djs55/fix-install-wizard

Fix the xenserver-install-wizard