Bug 24993: fix increment

Aparently ((i++)) isn't portable, changed for an admittedly uglier
but functional increment.

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Liz Rea <wizzyrea@gmail.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>

Signed-off-by: Joy Nelson <joy@bywatersolutions.com>

debian/scripts/koha-sip

@@ -152,7 +152,7 @@ restart_sip()
 
         MAX_ITERATION=10
         while is_sip_running ${name}; do
-            ((i++))
+            i=$((i+1))
             if [ $MAX_ITERATION -lt $i ]; then
                 break
             fi