Removes the errexit shell option from generate_network_config.sh (#276)

* Removes the bash -e shopt to avoid script exiting on error

The script runs a loop that checks for a files that may not exist. With -e set,
if it tries to list the files and they don't exist then the script exits. This
commit simply removes the -e shell option. There is likely some other
workaround, but this is pretty simple.

* Changes fq qdisc config script to look for carrier file

The file /sys/class/net/ethN/carrier is what the generate-network-config script
uses, and is probably more appropriate to the intention, and it was just an
oversight that this file didn't previously get changed too.

configs/stage3_ubuntu/opt/mlab/bin/configure_tc_fq.sh

@@ -1,5 +1,7 @@
 #!/bin/bash
 
+set -ux
+
 # This script writes out a Prometheus metric file which will be collected by the
 # node_exporter textfile collector. Make sure that METRIC_DIR exists.
 METRIC_DIR=/cache/data/node-exporter
@@ -23,8 +25,8 @@ function write_metric_file {
 # with a link. Set the default to eth0 as a fallback.
 DEVICE="eth0"
 for i in /sys/class/net/eth*; do
-  STATE=$(cat $i/operstate)
-  if [[ $STATE == "up" ]]; then
+  CARRIER=$(cat $i/carrier)
+  if [[ $CARRIER == "1" ]]; then
     DEVICE=$(basename $i)
     break
   fi

configs/stage3_ubuntu/opt/mlab/bin/generate_network_config.sh

@@ -4,7 +4,7 @@
 # writes a networkd configuration file for the static IP to the named file.
 # generate_network_config also sets the machine hostname.
 
-set -euxo pipefail
+set -ux
 
 OUTPUT=${1:?Please provide the name for writing config file}