MDEV-7139: Sporadic failure in innodb.innodb_corrupt_bit on P8

The testcase fails randomly due to ibuf merge happening in the background.
Fix not to do any merges with ibuf_debug enabled.

mysql-test/suite/innodb/t/innodb_corrupt_bit.test

@@ -3,11 +3,6 @@
 #
 -- source include/have_innodb.inc
 
-if (`select plugin_auth_version <= "5.5.40-MariaDB-36.1" from information_schema.plugins where plugin_name='innodb'`)
-{
-  --skip Not fixed in XtraDB as of 5.5.40-MariaDB-36.1 or earlier
-}
-
 # Issues with innodb_change_buffering_debug on Windows, so the test scenario
 # cannot be created on windows
 --source include/not_windows.inc
@@ -16,6 +11,7 @@ if (`select plugin_auth_version <= "5.5.40-MariaDB-36.1" from information_schema
 --source include/have_debug.inc
 
 -- disable_query_log
+call mtr.add_suppression("Flagged corruption of idx.*in CHECK TABLE");
 # This test setup is extracted from bug56680.test:
 # The flag innodb_change_buffering_debug is only available in debug builds.
 # It instructs InnoDB to try to evict pages from the buffer pool when
@@ -28,10 +24,10 @@ SET GLOBAL innodb_change_buffering_debug = 1;
 SET UNIQUE_CHECKS=0;
 
 CREATE DATABASE pad;
-let $i=345;
+let $i=338;
 while ($i)
 {
-  --eval CREATE TABLE pad.t$i (a INT PRIMARY KEY) ENGINE=InnoDB;
+--eval CREATE TABLE pad.t$i(a INT PRIMARY KEY)ENGINE=InnoDB;
   dec $i;
 }
 

storage/innobase/ibuf/ibuf0ibuf.c

@@ -2731,6 +2731,14 @@ ibuf_contract_for_n_pages(
 	ulint	n_bytes;
 	ulint	n_pag2;
 
+#if defined UNIV_DEBUG || defined UNIV_IBUF_DEBUG
+	if (ibuf_debug) {
+		return(0);
+	}
+#endif /* UNIV_DEBUG || UNIV_IBUF_DEBUG */
+
+
+
 	while (sum_pages < n_pages) {
 		n_bytes = ibuf_contract_ext(&n_pag2, sync);
 

storage/xtradb/ibuf/ibuf0ibuf.c

@@ -2775,6 +2775,12 @@ ibuf_contract_for_n_pages(
 	ulint	n_bytes;
 	ulint	n_pag2;
 
+#if defined UNIV_DEBUG || defined UNIV_IBUF_DEBUG
+	if (ibuf_debug) {
+		return(0);
+	}
+#endif /* UNIV_DEBUG || UNIV_IBUF_DEBUG */
+
 	while (sum_pages < n_pages) {
 		n_bytes = ibuf_contract_ext(&n_pag2, sync);