Avoid to block if ecole-dc is unreachable

mount_shares.sh

 #!/bin/bash
-
+max=3
+retries=0
 # Ensure ecole-dc is reachable before mounts
 while ! ping -c 1 ecole-dc  > /dev/null 2>&1
 do
-    echo "Cannot reach ecole-dc, waiting 10 sec"
-    sleep 10
+    if [ $retries -ge $max ]
+    then
+        exit
+    fi
+    retries=$(($retries+1))
+    echo "Cannot reach ecole-dc, waiting 5 sec"
+    sleep 5
 done
 
 #[ `grep -c '^//ecole-dc/' /etc/mtab` -gt 0 ] && exit 0