remove monitor if sstable write failed

In (almost) all SSTable write paths, we need to inform the monitor that
the write has failed as well. The monitor will remove the SSTable from
controller's tracking at that point.

Except there is one place where we are not doing that: streaming of big
mutations. Streaming of big mutations is an interesting use case, in
which it is done in 2 parts: if the writing of the SSTable fails right
away, then we do the correct thing.

But the SSTables are not commited at that point and the monitors are
still kept around with the SSTables until a later time, when they are
finally committed. Between those two points in time, it is possible that
the streaming code will detect a failure and manually call
fail_streaming_mutations(), which marks the SSTable for deletions. At
that point we should propagate that information to the monitor as well,
but we don't.

Fixes #3732 (hopefully)
Tests: unit (release)

Signed-off-by: Glauber Costa <glauber@scylladb.com>
Message-Id: <20181114213618.16789-1-glauber@scylladb.com>
(cherry picked from commit 9f403334c8)

database.cc

@@ -4191,6 +4191,7 @@ future<> table::fail_streaming_mutations(utils::UUID plan_id) {
     _streaming_memtables_big.erase(it);
     return entry->flush_in_progress.close().then([this, entry] {
         for (auto&& sst : entry->sstables) {
+            sst.monitor->write_failed();
             sst.sstable->mark_for_deletion();
         }
     });

database.hh

@@ -294,6 +294,8 @@ public:
 class table;
 using column_family = table;
 
+class database_sstable_write_monitor;
+
 class table : public enable_lw_shared_from_this<table> {
 public:
     struct config {
@@ -389,7 +391,7 @@ private:
     // plan memtables and the resulting sstables are not made visible until
     // the streaming is complete.
     struct monitored_sstable {
-        std::unique_ptr<sstables::write_monitor> monitor;
+        std::unique_ptr<database_sstable_write_monitor> monitor;
         sstables::shared_sstable sstable;
     };