Bug 21765: Make AutoUnsuspendReserves call Koha::Hold->resume

Bug 21765: Make AutoUnsuspendReserves call Koha::Hold->resume

This patch makes the mentioned method use the biult-in method for
resuming a suspended hold, instead of manually setting the specific
attributes using the accessors.

The side effect for this is that HoldsLog is now honoured.

This patchset also refactors the tests a bit so they rely on the exposed
methods and thus don't rely on specific implementation details (like
suspended hold means a date in suspended_until plus suspended=1).

To test:
- Apply the regression tests patch
- Run:
  $ kshell
 k$ prove t/db_dependent/Reserves/AutoUnsuspendReserves.t
=> FAIL: It fails loudly because things are done manually
- Apply this patch
- Run:
 k$ prove t/db_dependent/Reserves/AutoUnsuspendReserves.t
=> SUCCESS: Tests pass!

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>