Propagation: wrap commands in also_propagate array with MULIT/EXEC

Random command like SPOP with count is replicated as
some SREM operations, and store them in also_propagate
array to propagate after the call, but this would break
atomicity.

To keep the command's atomicity, wrap also_propagate
array with MULTI/EXEC.

src/multi.c

@@ -106,11 +106,13 @@ void discardCommand(client *c) {
 /* Send a MULTI command to all the slaves and AOF file. Check the execCommand
  * implementation for more information. */
 void execCommandPropagateMulti(client *c) {
-    robj *multistring = createStringObject("MULTI",5);
+    propagate(server.multiCommand,c->db->id,&shared.multi,1,
+              PROPAGATE_AOF|PROPAGATE_REPL);
+}
 
-    propagate(server.multiCommand,c->db->id,&multistring,1,
+void execCommandPropagateExec(client *c) {
+    propagate(server.execCommand,c->db->id,&shared.exec,1,
               PROPAGATE_AOF|PROPAGATE_REPL);
-    decrRefCount(multistring);
 }
 
 void execCommand(client *c) {