Bug 21230: Prevent Reserves.t to fail randomly

Bug 21230: Prevent Reserves.t to fail randomly

The following test can fail if the hold has been generated with found => 'W':
 #   Failed test 'No tests run for subtest "_koha_notify_reserve() tests"'
 #   at t/db_dependent/Reserves.t line 675.
Can't call method "to_address" on an undefined value at
t/db_dependent/Reserves.t line 661.
 # Looks like your test exited with 255 just after 56.

We should call AddReserve instead.

Test plan:
0. Do not apply this patch
1. Do the following change:
    my $hold = $builder->build({
            source => 'Reserve',
            value => {
               borrowernumber=>$hold_borrower,
               found => 'W', # This line is added, do not forget the comma above
            }
        });
2. Prove it makes the test fail
3. stash the changes and apply this patch
4. Make sure the tests pass

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>