um-service-cfg: Small improvements

Since kernel 5.10 upgrade, this script was actually not working
properly. The script is waiting on network.target to be ready, but
network.target does not mean that the route to user module is already
setup. And since with kernel 5.10 the route needs a bridge to be setup,
this takes a bit longer to be ready.

When there is no route to an IP address, ping does not wait the
specified timeout (-W) and returns immediately with an error. this was
leading to the 30 pings being done over a much smaller time period than
expected and therefore made the service fail before the route was setup.

Also in case the user module was not found, the service did not fail but
continued checking the port, which failed (of course) and the script was
then wrongly assuming the presence of an old UM.

BugzID: 81969

recipes-user-module/um-service-cfg/files/um-service-config.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/usr/bin/env bash
 
 UM_CONFIG_PATH=/etc/user-module
 UM_CONFIG_FILE=network.conf
@@ -37,16 +37,22 @@ done
 
 source $UM_CONFIG
 
-max_retry=30
+max_retry=15
 counter=0
 
 until [[ counter -ge $max_retry ]]
 do
   echo "Probing um. #$counter"
   ping -qc 1 -W 1 $USER_MODULE_ipv4_addr && break
+  sleep 1
   ((counter++))
 done
 
+if ! ping -qc 1 -W 1 $USER_MODULE_ipv4_addr
+then
+    echo "UM not reachable"
+    exit 1
+fi
 
 # Decide which config to load depending on the sw revision
 if `nc -z $USER_MODULE_ipv4_addr 7000` ; then