Bug 13380: Follow-up - only run database update, when it hasn't been run already

As the ORDER_CANCELLATION_REASON authorised value has been
backported to 3.18.5, we need to make sure that the database
update is only run once.

This patch adds a check for the existance of the authorised
value in order to decide if the databaes update can be run.

To test:
- Create a branch 3.19.00.016
- Make sure you have a few orders where the cancellationreason
  is set (cancel an order, enter a reason)
- Update your branch to master + this patch
- Run the web installer
- ORDER_CANCELLATION_REASON authorised value category is created
- Reset your system preference Version to 3.19.00.015
- Run database update again - no changes are made, all is fine

Or:
- Create a branch 3.18.04 with cancelled orders
- Update to latest 3.18.x
- Make sure ORDER_CANCELLATION_REASON has been created
- Dump database
- Switch to master without this patch
- Run update - verify more O_C_R were created (bad)
- Load database
- Update to master with this patch
- All should be fine

Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>

installer/data/mysql/updatedatabase.pl

@@ -9876,6 +9876,8 @@ if ( CheckVersion($DBversion) ) {
 
 $DBversion = "3.19.00.016";
 if(CheckVersion($DBversion)) {
+    my @order_cancellation_reason = $dbh->selectrow_array("SELECT count(*) FROM authorised_values WHERE category='ORDER_CANCELLATION_REASON'");
+    if ($order_cancellation_reason[0] == 0) {
         $dbh->do(q{
             INSERT INTO authorised_values (category, authorised_value, lib) VALUES
              ('ORDER_CANCELLATION_REASON', 0, 'No reason provided'),
@@ -9906,6 +9908,11 @@ if(CheckVersion($DBversion)) {
             $i++;
         }
         print "Upgrade to $DBversion done (Bug 13380: Add the ORDER_CANCELLATION_REASON authorised value)\n";
+    }
+    else {
+        print "Upgrade to $DBversion done (Bug 13380: ORDER_CANCELLATION_REASON authorised value already existed from earlier update!)\n";
+    }
+
     SetVersion($DBversion);
 }