xenapi: cleanup VM Installation

VM installation created a machine with multiple network interfaces. This
is a needless complexity at that point, we only need one interface. This
change removes the complex network interface setup from
install-os-vpx.sh script, so that only one network interface is created,
which is connected to the selected network (management by default). This
change also removes a lot of non-used code from install-os-vpx.sh
Specify the network to be used for ubuntu netinstall with:

    UBUNTU_INST_BRIDGE_OR_NET_NAME

defaults to $MGT_BRIDGE_OR_NET_NAME.

This change also includes:
 - use precise as default

Related to blueprint xenapi-devstack-cleanup

Change-Id: Ib0a0a316e849f2c2651305ea657c84820cd2bb3b
diff --git a/tools/xen/xenrc b/tools/xen/xenrc
index 2bd7be7..afa3d32 100644
--- a/tools/xen/xenrc
+++ b/tools/xen/xenrc
@@ -60,8 +60,8 @@
 PUB_NETMASK=${PUB_NETMASK:-255.255.255.0}
 
 # Ubuntu install settings
-UBUNTU_INST_RELEASE="oneiric"
-UBUNTU_INST_TEMPLATE_NAME="Ubuntu 11.10 (64-bit) for DevStack"
+UBUNTU_INST_RELEASE="precise"
+UBUNTU_INST_TEMPLATE_NAME="Ubuntu 12.04 (64-bit) for DevStack"
 # For 12.04 use "precise" and update template name
 # However, for 12.04, you should be using
 # XenServer 6.1 and later or XCP 1.6 or later
@@ -72,11 +72,8 @@
 UBUNTU_INST_HTTP_PROXY=""
 UBUNTU_INST_LOCALE="en_US"
 UBUNTU_INST_KEYBOARD="us"
-# network configuration for ubuntu netinstall.
-# TODO(matelakat): get rid of legacy network interfaces
-# specify "eth2" to use the management network
-# specify "eth3" to use the public network
-UBUNTU_INST_IFACE="eth2"
+# network configuration for ubuntu netinstall
+UBUNTU_INST_BRIDGE_OR_NET_NAME=${UBUNTU_INST_BRIDGE_OR_NET_NAME:-"$MGT_BRIDGE_OR_NET_NAME"}
 UBUNTU_INST_IP="dhcp"
 UBUNTU_INST_NAMESERVERS=""
 UBUNTU_INST_NETMASK=""