MDEV-11454: Improve test case innodb_buffer_pool_dump_pct

Based off feedback from Marko Mäkelä:
* Don't set timeouts on restart.
* Use innodb_fast_shutdown=0

Also:

Set innodb_buffer_pool_instances=1 - adds predicability to tests
- if a biased pool is used less pages could be saved.
Signed-off-by: Daniel Black <daniel.black@au.ibm.com>

mysql-test/suite/sys_vars/r/innodb_buffer_pool_dump_pct_function.result

-SET GLOBAL innodb_buffer_pool_dump_pct=25, global innodb_buffer_pool_dump_at_shutdown=1;;
 # populate with data
 CREATE TABLE t1 (
 c01 blob, c02 blob, c03 blob, c04 blob, c05 blob,
@@ -31,6 +30,7 @@ INSERT INTO t1 VALUES (@a,@a,@a,@a,@a,
 @a,@a,@a,@a
 );
 insert into t1 select * from t1;
+SET GLOBAL innodb_buffer_pool_dump_pct=25,GLOBAL innodb_fast_shutdown=0, GLOBAL innodb_buffer_pool_dump_at_shutdown=1;
 # Restart server
 SET GLOBAL innodb_buffer_pool_load_now=1;
 # Case 1: Limit from innodb_buffer_pool_dump_pct

mysql-test/suite/sys_vars/t/innodb_buffer_pool_dump_pct_function.opt

@@ -2,4 +2,5 @@
 --loose-innodb_buffer_pool_load_at_startup=0
 --loose-innodb_buffer_pool_dump_at_shutdown=0
 --loose-innodb-buffer-pool-size=8M
+--loose-innodb-buffer-pool-instances=1
 --loose-innodb-page-size=16k

mysql-test/suite/sys_vars/t/innodb_buffer_pool_dump_pct_function.test

@@ -7,10 +7,6 @@
 
 -- source include/have_innodb.inc
 
---let $PCT=25
-
---eval SET GLOBAL innodb_buffer_pool_dump_pct=$PCT, global innodb_buffer_pool_dump_at_shutdown=1;
-
 --echo # populate with data
 
 CREATE TABLE t1 (
@@ -49,11 +45,12 @@ insert into t1 select * from t1;
 
 --let $blob_pages=`select count(*)  from information_schema.INNODB_BUFFER_PAGE WHERE PAGE_TYPE='BLOB' group by PAGE_TYPE`
 
+--let $PCT=25
+--eval SET GLOBAL innodb_buffer_pool_dump_pct=$PCT,GLOBAL innodb_fast_shutdown=0, GLOBAL innodb_buffer_pool_dump_at_shutdown=1
+
 # Dump on shutdown has been set - shutdown now
 
 --echo # Restart server
---let $shutdown_timeout= 10
---let $allow_rpl_inited= 1
 --source include/restart_mysqld.inc
 
 SET GLOBAL innodb_buffer_pool_load_now=1;