compaction_manager: Don't swallow exception in procedure used by reshape and resharding

run_custom_job() was swallowing all exceptions, which is definitely
wrong because failure in a resharding or reshape would be incorrectly
interpreted as success, which means upper layer will continue as if
everything is ok. For example, ignoring a failure in resharding could
result in a shared sstable being left unresharded, so when that sstable
reaches a table, scylla would abort as shared ssts are no longer
accepted in the main sstable set.
Let's allow the exception to be propagated, so failure will be
communicated, and resharding and reshape will be all or nothing, as
originally intended.

Fixes #8657.

Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <20210515015721.384667-1-raphaelsc@scylladb.com>

sstables/compaction_manager.cc

@@ -314,6 +314,7 @@ future<> compaction_manager::run_custom_job(column_family* cf, sstring name, non
             cmlog.info("{} was abruptly stopped, reason: {}", name, e.what());
         } catch (...) {
             cmlog.error("{} failed: {}", name, std::current_exception());
+            throw;
         }
     });
     return task->compaction_done.get_future().then([task] {});