Bug 11891: set up tests to require that Koha::Database uses same DB handle as C4::Context

This patch removes changes in two cases to work around the fact that
Koha::Database and C4::Context were not using the same DBI database
handle.

To test:

[1] Run prove -v t/db_dependent/ILSDI_Services.t and
    prove -v t/db_dependent/Items.t.  Both tests
    should fail.
[2] Apply the main patches and run step 1 again.  This
    time, both tests should pass.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>
Bug 11891 - Make Koha::Schema use C4::Context->dbh

Right now there is no connection between the database handles used by
C4::Context::dbh and Koha::Datbase/Schema. This makes it impossible to
use transactions in unit tests to temporarily modify the database to
test subroutines that take advantage of Koha::Database. This patch fixes
that issue.

Test Plan:
1) Apply this patch
2) prove -v t/db_dependent/ILSDI_Services.t and
   prove -v t/db_dependent/Items.t and
   prove -v t/db_dependent/Circulation_issue.t should
   all start passing

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>
Bug 11891: (follow-up) remove custom storage class

For now, just rely on the normal DBIx::Class cleanup handler;
otherwise, the following warning is displayed in logs:

  (in cleanup) Can't locate object method "_preserve_foreign_dbh" via package "Koha::Storage" at .../Koha/Storage.pm

Using the default DBIC storage class also means that we
don't have to manually do things like set the SQL limit dialect;
meaning that we don't get the following warning message:

  DBIx::Class::ResultSet::find(): Your storage class (Koha::Storage) does
  not set sql_limit_dialect and you have not supplied an explicit
  limit_dialect in your connection_info. DBIC will attempt to use the
  GenericSubQ dialect, which works on most databases but can be (and
  often is) painfully slow. Please file an RT ticket against
  'Koha::Storage' . at /home/gmc/koha/C4/Members.pm line 840

Test plan: same as main patch

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>
Bug 11891: (follow-up) set DBIC storage flags correctly

Since we're passing an existing DBI database handle to
DBIC, and that handle doesn't have RaiseError set to true
by default, don't let DBIC override that -- for now.

Test plan: verify that the DB-dependent test suite passes.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>