crimson/os/seastore: fix incorrect total space reporting when using multiple shards in RBM

This commit fixes incorrect total space reporting when using multiple shards in RBM.
Only reporting is incorrect, while underlying RBM mechanism works correctly.

Signed-off-by: Myoungwon Oh <[email protected]>

Author: myoungwon

src/crimson/os/seastore/async_cleaner.h

@@ -1762,7 +1762,8 @@ class RBMCleaner : public AsyncCleaner {
     auto rbs = rb_group->get_rb_managers();
     size_t total = 0;
     for (auto p : rbs) {
-      total += p->get_device()->get_available_size();
+      total += p->get_size();
+      total += p->get_journal_size();
     }
     return total;
   }