[master] Merge branch 'trac3427' (logging configuration in kea4,kea6,d2)
Conflicts: ChangeLog configure.ac src/bin/dhcp4/kea_controller.cc src/bin/dhcp6/kea_controller.cc src/bin/dhcp6/main.cc src/lib/log/logger_manager.cc src/lib/log/logger_unittest_support.cc src/lib/log/logger_unittest_support.h