raft: fsm: add empty check for max_read_id_with_quorum

Updated the empty() function in the struct fsm_output to include the
max_read_id_with_quorum field when checking whether the fsm output is
empty or not. The change was made in order maintain consistency with the
codebase and adding completeness to the empty check. This change has no
impact on other parts of the codebase.

Closes #13656

raft/fsm.hh

@@ -47,7 +47,7 @@ struct fsm_output {
         return !term_and_vote &&
             log_entries.size() == 0 && messages.size() == 0 &&
             committed.size() == 0 && !snp && snps_to_drop.empty() &&
-            !configuration;
+            !configuration && !max_read_id_with_quorum;
     }
 };
 
@@ -654,4 +654,3 @@ void fsm::step(server_id from, Message&& msg) {
 }
 
 } // namespace raft
-