installer: exit if no default iface or IP can be determined

Change-Id: Iddaefc40007c6a6a739b42f32f0a698c1682b448
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>

installers/full_install_osm.sh

@@ -724,7 +724,9 @@ function install_lightweight() {
     LWTEMPDIR="$(mktemp -d -q --tmpdir "installosmlight.XXXXXX")"
     trap 'rm -rf "${LWTEMPDIR}"' EXIT
     DEFAULT_IF=`route -n |awk '$1~/^0.0.0.0/ {print $8}'`
+    [ -z "$DEFAULT_IF" ] && FATAL "Not possible to determine the interface with the default route 0.0.0.0"
     DEFAULT_IP=`ip -o -4 a |grep ${DEFAULT_IF}|awk '{split($4,a,"/"); print a[1]}'`
+    [ -z "$DEFAULT_IP" ] && FATAL "Not possible to determine the IP address of the interface with the default route"
     DEFAULT_MTU=$(ip addr show ${DEFAULT_IF} | perl -ne 'if (/mtu\s(\d+)/) {print $1;}')
     if [ -z "$INSTALL_NOLXD" ]; then
         need_packages_lw="lxd"