MDEV-10161: wsrep_sync_wait not enabled when set to 1 in config file

Since wsrep_sync_wait & wsrep_causal_reads variables are related,
they are always kept in sync whenever one of them changes.
Same is tried on server start, where wsrep_sync_wait get updated
based on wsrep_causal_reads' value. But, since wsrep_causal_reads
is OFF by default, wsrep_sync_wait's value gets modified and loses
its WSREP_SYNC_WAIT_BEFORE_READ bit.

Fixed by syncing wsrep_sync_wait & wsrep_causal_reads values
individually on server start in mysqld_get_one_option() based
on command line arguments used.

mysql-test/suite/galera/galera_2nodes.cnf

@@ -9,7 +9,6 @@ default-storage-engine=innodb
 wsrep-provider=@ENV.WSREP_PROVIDER
 wsrep_node_address=127.0.0.1
 # enforce read-committed characteristics across the cluster
-wsrep-causal-reads=ON
 wsrep-sync-wait=7
 
 [mysqld.1]

mysql-test/suite/galera/r/galera_var_sync_wait.result

@@ -1,3 +1,12 @@
+#
+# MDEV-10161: wsrep_sync_wait not enabled when set to 1 in config file
+#
+SELECT @@global.wsrep_sync_wait;
+@@global.wsrep_sync_wait
+7
+SELECT @@global.wsrep_causal_reads;
+@@global.wsrep_causal_reads
+1
 CREATE TABLE t1 (f1 INT PRIMARY KEY) Engine=InnoDB;
 SET GLOBAL wsrep_sync_wait = 1;
 SHOW TABLES LIKE '%t1';

mysql-test/suite/galera/t/galera_var_sync_wait.test

@@ -5,6 +5,13 @@
 --source include/galera_cluster.inc
 --source include/have_innodb.inc
 
+--echo #
+--echo # MDEV-10161: wsrep_sync_wait not enabled when set to 1 in config file
+--echo #
+# galera_2nodes.cnf sets wsrep_sync_wait to 7
+SELECT @@global.wsrep_sync_wait;
+SELECT @@global.wsrep_causal_reads;
+
 --let $wsrep_sync_wait_orig = `SELECT @@wsrep_sync_wait`
 
 --connection node_1