fix(telegraf/rootfs/start-telegraf): address shellcheck/style err

Author: vdice

telegraf/rootfs/start-telegraf

@@ -31,7 +31,7 @@ if [ -n "$ENABLE_PROMETHEUS" ]; then
 fi
 
 # if the influxdb url does not start with a quote, assume it's singular and quote it
-if [ ${INFLUXDB_URLS:0:1} != "\"" ]; then
+if [ "${INFLUXDB_URLS:0:1}" != "\"" ]; then
   export INFLUXDB_URLS="\"$INFLUXDB_URLS\""
 fi