crimson/osd: introduce more asserts to the Watch timeout handling.

Signed-off-by: Radoslaw Zarzynski <rzarzyns@redhat.com>

src/crimson/osd/ops_executer.cc

@@ -181,6 +181,7 @@ OpsExecuter::watch_ierrorator::future<> OpsExecuter::do_op_watch_subop_watch(
       return seastar::now();
     },
     [] (auto&& ctx, ObjectContextRef obc, Ref<PG> pg) {
+      assert(pg);
       auto [it, emplaced] = obc->watchers.try_emplace(ctx.key, nullptr);
       if (emplaced) {
         const auto& [cookie, entity] = ctx.key;

src/crimson/osd/watch.cc

@@ -182,6 +182,7 @@ void Watch::cancel_notify(const uint64_t notify_id)
 
 void Watch::do_watch_timeout(Ref<PG> pg)
 {
+  assert(pg);
   auto [op, fut] = pg->get_shard_services().start_operation<WatchTimeoutRequest>(
     shared_from_this(), pg);
   std::ignore = std::move(fut).then([op=std::move(op), this] {

src/crimson/osd/watch.h

@@ -61,6 +61,7 @@ public:
       winfo(winfo),
       entity_name(entity_name),
       timeout_timer([this, pg=std::move(pg)] {
+        assert(pg);
         return do_watch_timeout(pg);
       }) {
   }