MDEV-7656 init_file option does not allow changing passwords

allow SET PASSWORD from  bootstrap and init-file

mysql-test/r/init_file_set_password-7656.result

@@ -0,0 +1,8 @@
+create user foo@localhost;
+select user,host,password from mysql.user where user='foo';
+user	host	password
+foo	localhost	
+select user,host,password from mysql.user where user='foo';
+user	host	password
+foo	localhost	*94BDCEBE19083CE2A1F959FD02F964C7AF4CFC29
+drop user foo@localhost;

mysql-test/t/init_file_set_password-7656.test

@@ -0,0 +1,26 @@
+#
+# MDEV-7656 init_file option does not allow changing passwords
+#
+--source include/not_embedded.inc
+
+create user foo@localhost;
+
+select user,host,password from mysql.user where user='foo';
+
+--write_file $MYSQLTEST_VARDIR/init.file
+grant all on *.* to foo@localhost identified by 'test';
+EOF
+
+--enable_reconnect
+
+--exec echo "wait" > $MYSQLTEST_VARDIR/tmp/mysqld.1.expect
+
+--shutdown_server 10
+--source include/wait_until_disconnected.inc
+
+--exec echo "restart:--init-file=$MYSQLTEST_VARDIR/init.file  " > $MYSQLTEST_VARDIR/tmp/mysqld.1.expect
+
+--source include/wait_until_connected_again.inc
+select user,host,password from mysql.user where user='foo';
+
+drop user foo@localhost;

sql/sql_acl.cc

@@ -2558,7 +2558,8 @@ int check_change_password(THD *thd, const char *host, const char *user,
     my_error(ER_OPTION_PREVENTS_STATEMENT, MYF(0), "--skip-grant-tables");
     return(1);
   }
-  if (!thd->slave_thread && !thd->security_ctx->priv_user[0])
+  if (!thd->slave_thread && !thd->security_ctx->priv_user[0] &&
+      !in_bootstrap)
   {
     my_message(ER_PASSWORD_ANONYMOUS_USER, ER(ER_PASSWORD_ANONYMOUS_USER),
                MYF(0));