Some of the calls inside the `raft_group0_client::start_operation()`
method were missing the abort source parameter. This caused the repair
test to be stuck in the shutdown phase - the abort source has been
triggered, but the operations were not checking it.
This was in particular the case of operations that try to take the
ownership of the raft group semaphore (`get_units(semaphore)`) - these
waits should be cancelled when the abort source is triggered.
This should fix the following tests that were failing in some percentage
of dtest runs (about 1-3 of 100):
* TestRepairAdditional::test_repair_kill_1
* TestRepairAdditional::test_repair_kill_3
Fixesscylladb/scylladb#19223
(cherry picked from commit 5dfc50d354)
b99d87863d