Bug 16829: Unit tests for logaction's 'interface parameter'

Bug 16829: Unit tests for logaction's 'interface parameter'

This patch introduces tests for the new 'interface' parameter for the
C4::Log::logaction and C4::Log::GetLogs functions.

In logaction, it falls back to C4::Context->interface if ommited.

To test:
- Run
  $ prove t/db_dependent/Log.t
=> SUCCESS: Tests pass
- Sign off

Sponsored-by: NEKLS
Signed-off-by: Nicole C Engard <nengard@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>