Added test: set var @a via select @@server_id

Added test: set  var @a via select @@server_id

server/modules/routing/readwritesplit/test/rwsplit.sh

@@ -37,3 +37,14 @@ if [ "$a" != "$TRETVAL" ]; then
 else 
         echo "$TINPUT PASSED">>$TLOG ; 
 fi
+
+# set a var via SELECT INTO @, get data from master, returning server-id: put master server-id value in TRETVAL
+TINPUT=select_for_var_set.sql
+TRETVAL=2
+
+a=`$RUNCMD < ./$TINPUT`
+if [ "$a" != "$TRETVAL" ]; then 
+        echo "$TINPUT FAILED, return value $a when $TRETVAL was expected">>$TLOG; 
+else 
+        echo "$TINPUT PASSED">>$TLOG ; 
+fi