Bug#49329 example (and other) engines use wrong collation for open tables hash

This fix changes the character set used within the
IBMDB2I handler to hash table names to information
about open tables. Previously, tables with names
that differed only in letter case would hash to the
same data structure. This caused incorrect behavior
or errors when two such tables were in use simultaneously.

mysql-test/suite/ibmdb2i/r/ibmdb2i_bug_49329.result

+create table ABC (i int) engine=ibmdb2i;
+insert into ABC values(1);
+create table abc (i int) engine=ibmdb2i;
+insert into abc values (2);
+select * from ABC;
+i
+1
+drop table ABC;
+drop table abc;

mysql-test/suite/ibmdb2i/t/ibmdb2i_bug_49329.test

+source suite/ibmdb2i/include/have_ibmdb2i.inc;
+source include/have_case_sensitive_file_system.inc;
+
+create table ABC (i int) engine=ibmdb2i;
+insert into ABC values(1);
+create table abc (i int) engine=ibmdb2i;
+insert into abc values (2);
+select * from ABC;
+drop table ABC;
+drop table abc;

storage/ibmdb2i/ha_ibmdb2i.cc

@@ -284,7 +284,7 @@ static int ibmdb2i_init_func(void *p)
   was_ILE_inited = false;
   ibmdb2i_hton= (handlerton *)p;
   VOID(pthread_mutex_init(&ibmdb2i_mutex,MY_MUTEX_INIT_FAST));
-  (void) hash_init(&ibmdb2i_open_tables,system_charset_info,32,0,0,
+  (void) hash_init(&ibmdb2i_open_tables,table_alias_charset,32,0,0,
                    (hash_get_key) ibmdb2i_get_key,0,0);
 
   ibmdb2i_hton->state=   SHOW_OPTION_YES;