Testing msi: Add retries if necessary

Hoping this will fix the annoying problems on Windows Jenkins.

src/ioc/dbtemplate/test/msi.plt

@@ -58,5 +58,19 @@ sub msi {
     my ($args) = @_;
     my $exe = ($^O eq 'MSWin32') || ($^O eq 'cygwin') ? '.exe' : '';
     my $msi = "./msi-copy$exe";
-    return `$msi $args`;
+    my $result;
+    if ($args =~ m/-o / && $args !~ m/-D/) {
+        # An empty result is expected
+        $result = `$msi $args`;
+    }
+    else {
+        # Try up to 5 times, sometimes msi fails on Windows
+        my $count = 5;
+        do {
+            $result = `$msi $args`;
+            print "# result of '$msi $args' empty, retrying\n"
+                if $result eq '';
+        } while ($result eq '') && (--$count > 0);
+    }
+    return $result;
 }