replace is_rpi with rpi_model

scripts/local_facts.fact

@@ -56,6 +56,12 @@ else
     XO_VERSION="none"
 fi
 
+if [ -f /proc/device-tree/model ]; then
+    RPI_VERSION=`cat /proc/device-tree/model`
+else
+    RPI_VERSION="none"
+fi
+
 ANSIBLE_VERSION=$(ansible --version|head -n 1|cut -f 2 -d " ")
 
 if [ ! x$DHCPCD_PATH = x ]; then
@@ -77,6 +83,7 @@ cat <<EOF
 "iiab_branch"             : "$BRANCH",
 "iiab_commit"             : "$COMMIT",
 "xo_model"                : "$XO_VERSION",
+"rpi_model"               : "$RPI_VERSION",
 "ansible_version"         : "$ANSIBLE_VERSION",
 "os"                      : "$OS",
 "os_ver"                  : "$OS_VER"}