MXS-2427 Extend namedserverfilter test

Tests with two targets.

maxscale-system-test/cnf/maxscale.cnf.template.namedserverfilter

@@ -5,8 +5,8 @@ log_warning=1
 [namedserverfilter]
 type=filter
 module=namedserverfilter
-match=SELECT
-server=server2
+match01=^SELECT
+target01=server2,server3
 
 [MySQL Monitor]
 type=monitor
@@ -19,9 +19,7 @@ monitor_interval=1000
 [RW Split Router]
 type=service
 router=readwritesplit
-
-# Mixing the order of slaves will make server3 the first slave server
-servers=server1,server3,server2,server4
+servers=server1,server2,server3,server4
 user=maxskysql
 password=skysql
 filters=namedserverfilter