fix extension_based_table_discovery for partitioned tables

typo. the code was not matching the comment

mysql-test/suite/archive/partition_archive.result

@@ -153,3 +153,9 @@ t1	CREATE TABLE `t1` (
 PARTITIONS 5 */
 #Cleanup.
 DROP TABLE t1;
+create database mysqltest1;
+create table mysqltest1.t1 (a int not null, b int not null) engine=archive
+partition by list(a) subpartition by hash(b)
+(partition p1 values in (1),
+partition p2 values in (2));
+drop database mysqltest1;

mysql-test/suite/archive/partition_archive.test

@@ -147,3 +147,10 @@ SHOW CREATE TABLE t1;
 
 --echo #Cleanup.
 DROP TABLE t1;
+
+create database mysqltest1;
+create table mysqltest1.t1 (a int not null, b int not null) engine=archive
+  partition by list(a) subpartition by hash(b)
+  (partition p1 values in (1),
+   partition p2 values in (2));
+drop database mysqltest1;

sql/discover.cc

@@ -199,7 +199,7 @@ int extension_based_table_discovery(MY_DIR *dirp, const char *ext_meta,
   end= cur + dirp->number_of_files;
   while (cur < end)
   {
-    char *octothorp= strrchr(cur->name + 1, '#');
+    char *octothorp= strchr(cur->name + 1, '#');
     char *ext= strchr(octothorp ? octothorp : cur->name, FN_EXTCHAR);
 
     if (ext)