BibIndex: minor engine refactoring
- Refactors code in update_virtual_indexes and remove_dependent_indexes functions.
- Fixes a problem occurring when user removes depenednt index both in admin interface and through CLI.
Signed-off-by: Grzegorz Szpura <grzegorz.szpura@cern.ch>
Tested-by: Tibor Simko <tibor.simko@cern.ch>