Bug 19977: Open only .pref files in Local Use tab (sysprefs)

Test plan:
1. Open .../prog/en/modules/admin/preferences/circulation.pref
with vim (check that it creates a .circulation.pref.swp in the same
directory)
2. Go to the "Local Use" tab in admin/systempreferences.pl
3. Confirm that the page works normally

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>

admin/systempreferences.pl

@@ -391,7 +391,7 @@ sub get_prefs_from_files {
                         '/prog/en/modules/admin/preferences';
     # Get all .pref file names
     opendir ( my $fh, $path_pref_en );
-    my @pref_files = grep { /.pref/ } readdir($fh);
+    my @pref_files = grep { /.pref$/ } readdir($fh);
     close $fh;
 
     my @names = ();