* Disallow setting wsrep_on = 1 if wsrep_provider is unset. Also, move
  wsrep_on_basic from sys_vars to wsrep suite: this test now requires
  to run with wsrep_provider set
* Disallow setting @@session.wsrep_on = 1 when @@global.wsrep_on = 0
* Handle the case where a new connection turns @@global.wsrep_on from
  off to on. In this case we would miss a call to wsrep_open, causing
  unexpected states in wsrep::client_state (causing assertions).
* Disable wsrep.MDEV-22443 because it is no longer possible to enable
  wsrep_on, if server is started with wsrep_provider='none'
Reviewed-by: Jan Lindström <jan.lindstrom@mariadb.com>