Bug 18243: 16034 follow-up: better handling of absence of WebService::ILS::OverDrive...

Bug 18243: 16034 follow-up: better handling of absence of WebService::ILS::OverDrive::Patron at testing

To test:
1 - Make sure you don't have WebService::ILS::OverDrive::Patron
installed
2 - prove t/Koha_ExternalContent_OverDrive.t
3 - You should get a failure to load module and tests are skipped
4 - Apply patch
5 - prove t/Koha_ExternalContent_OverDrive.t
6 - Module is not loaded, test are skipped

Fixed small typo 'cannot filnd' -> 'cannot find'
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>