Test galera_suspend_slave checks that after suspending a galera
node, like this:
```
--perl
my $pid_filename = $ENV{'NODE_2_PIDFILE'};
my $mysqld_pid = `cat $pid_filename`;
chomp($mysqld_pid);
system("kill -SIGSTOP $mysqld_pid");
exit(0);
EOF
```
the remaining one node cluster is no longer able to successfully
INSERT new rows:
```
--error ER_UNKNOWN_COM_ERROR,ER_LOCK_WAIT_TIMEOUT,ER_LOCK_DEADLOCK,ER_ERROR_DURING_COMMIT
INSERT INTO t1 VALUES (1);
```
On rare occasions when the system is overloaded, it appears that
suspending the process with ```system("kill -SIGSTOP $mysqld_pid")```
takes some time, enough for the subsequent INSERT to succeed. In which
case the test fails because it rightly expects the INSERT to fail.
To fix the problem, the patch makes sure that the cluster has shrinked
to one node, before trying to INSERT the new value.
(MDEV-8617: Post-fix for 10.1)
* Reset THD's PS members before returning when node is
not ready
* Add CF_SKIP_WSREP_CHECK flag to COM_STMT_XXX commands
* Skip TO replication of COM_STMT_PREPAREs for MyISAM
* Updated tests
