MDEV-18265: Replace deprecated variable debug to debug_dbug on Galera tests

	deleted:    mysql-test/suite/galera/r/MW-86.result
	deleted:    mysql-test/suite/galera/r/mysql-wsrep#216.result
	modified:   mysql-test/suite/galera/t/GCF-1081.test
	modified:   mysql-test/suite/galera_3nodes_sr/r/GCF-832.result
	modified:   mysql-test/suite/galera_3nodes_sr/t/GCF-810A.test
	modified:   mysql-test/suite/galera_3nodes_sr/t/GCF-810B.test
	modified:   mysql-test/suite/galera_3nodes_sr/t/GCF-810C.test
	modified:   mysql-test/suite/galera_3nodes_sr/t/GCF-832.test
	modified:   mysql-test/suite/galera_sr/r/mysql-wsrep-features#35.result
	modified:   mysql-test/suite/galera_sr/t/mysql-wsrep-features#35.test