MDEV-26322 Last binlog file and position are "empty" in mariabackup --prepare output

The issue is caused by 59a0236da4 commit.
The initial intention of the commit was to speed up
"mariabackup --prepare".

The call stack of binlog position reading is the following:
▾ trx_rseg_mem_restore
  ▾ trx_rseg_array_init
      ▾ trx_lists_init_at_db_start
            ▸ srv_start
Both trx_lists_init_at_db_start() and trx_rseg_mem_restore() contain
special cases for srv_operation == SRV_OPERATION_RESTORE condition, and
on this condition only rseg headers are read to parse binlog position.
Performance impact is not so big.

The solution is to revert 59a0236da4.

mysql-test/suite/mariabackup/binlog.result

@@ -3,6 +3,6 @@ INSERT INTO t VALUES(1);
 SHOW VARIABLES like 'log_bin';
 Variable_name	Value
 log_bin	ON
-FOUND 1 /Last binlog file .*, position .*/ in current_test
+FOUND 1 /Last binlog file .+, position \d+/ in current_test
 # expect FOUND
 DROP TABLE t;

mysql-test/suite/mariabackup/binlog.test

@@ -15,7 +15,7 @@ exec $XTRABACKUP --defaults-file=$MYSQLTEST_VARDIR/my.cnf  --backup --target-dir
 exec $XTRABACKUP --prepare --binlog-info=1 --target-dir=$basedir ;
 
 let SEARCH_FILE=$MYSQLTEST_VARDIR/log/current_test;
---let SEARCH_PATTERN= Last binlog file .*, position .*
+--let SEARCH_PATTERN= Last binlog file .+, position \d+
 --source include/search_pattern_in_file.inc
 --echo # expect FOUND
 

storage/innobase/srv/srv0start.cc

@@ -1479,9 +1479,6 @@ file_checked:
 			if (err != DB_SUCCESS) {
 				return srv_init_abort(err);
 			}
-			if (srv_operation == SRV_OPERATION_RESTORE) {
-				break;
-			}
 			err = trx_lists_init_at_db_start();
 			if (err != DB_SUCCESS) {
 				return srv_init_abort(err);