recovery: remove yields from index build and format check

Iproto already listens for requests during recovery, so yielding at this
point of time allows such early requests, which arrived during recovery,
be processed while data is in unfinished state. This caused box/net.box
test failures, and is potentially harmful.
Besides, there is no need to yield during recovery.

Closes #4273

src/box/memtx_space.c

@@ -47,6 +47,10 @@
  * Yield every 1K tuples while building a new index or checking
  * a space format. In debug mode yield more often for testing
  * purposes.
+ *
+ * Yields do not happen during recovery. At this point of time
+ * iproto aready accepts requests, and yielding would allow them
+ * to be proccessed while data is not fully recovered.
  */
 #ifdef NDEBUG
 enum { MEMTX_DDL_YIELD_LOOPS = 1000 };
@@ -884,6 +888,7 @@ memtx_space_check_format(struct space *space, struct tuple_format *format)
 	if (it == NULL)
 		return -1;
 
+	struct memtx_engine *memtx = (struct memtx_engine *)space->engine;
 	struct memtx_ddl_state state;
 	state.format = format;
 	state.cmp_def = pk->def->key_def;
@@ -905,7 +910,8 @@ memtx_space_check_format(struct space *space, struct tuple_format *format)
 		rc = tuple_validate(format, tuple);
 		if (rc != 0)
 			break;
-		if (++count % MEMTX_DDL_YIELD_LOOPS == 0) {
+		if (++count % MEMTX_DDL_YIELD_LOOPS == 0 &&
+		    memtx->state == MEMTX_OK) {
 			state.cursor = tuple;
 			tuple_ref(state.cursor);
 			fiber_sleep(0);
@@ -1033,6 +1039,7 @@ memtx_space_build_index(struct space *src_space, struct index *new_index,
 	if (it == NULL)
 		return -1;
 
+	struct memtx_engine *memtx = (struct memtx_engine *)src_space->engine;
 	struct memtx_ddl_state state;
 	state.index = new_index;
 	state.format = new_format;
@@ -1079,7 +1086,8 @@ memtx_space_build_index(struct space *src_space, struct index *new_index,
 		 */
 		if (new_index->def->iid == 0)
 			tuple_ref(tuple);
-		if (++count % MEMTX_DDL_YIELD_LOOPS == 0) {
+		if (++count % MEMTX_DDL_YIELD_LOOPS == 0 &&
+		    memtx->state == MEMTX_OK) {
 			/*
 			 * Remember the latest inserted tuple to
 			 * avoid processing yet to be added tuples