Export to local disk instead of backup medium.

The export directory will then be backed up normally, which is a simple
copy operation, while exporting all sessions is expensive and should not
be repeated for every new backup medium.

lib/Simba/CA.pm

@@ -835,7 +835,7 @@ sub adjust_partitions {
 sub export {
     my ($self) = @_;
     my $dbh = $self->{dbh};
-    my $exportdir = $self->basedir . "/export";
+    my $exportdir = "/var/lib/simba/export";
     mkdir($exportdir);
 
     my $sessions = $dbh->selectcol_arrayref("select id from sessions order by id");