MXS-1300: Add more MaxCtrl cluster tests

Added scripts that start two MaxScale on the same machine. This allows the
cluster synchronization commands to be tested locally.

test/start_double_maxscale.sh

@@ -0,0 +1,33 @@
+#!/bin/bash
+
+#
+# This script is run before each test block. It starts two MaxScales and waits
+# for them to become responsive.
+#
+
+maxscaledir=$MAXSCALE_DIR
+
+test -z "$MAXSCALE_DIR" && exit 1
+
+# Start MaxScale
+$maxscaledir/bin/maxscale -lstdout -df $maxscaledir/maxscale.cnf >& $maxscaledir/maxscale1.output &
+
+# Wait for the first MaxScale to start
+for ((i=0;i<60;i++))
+do
+    $maxscaledir/bin/maxadmin help >& /dev/null && break
+    sleep 0.1
+done
+
+# Start a second maxscale
+$maxscaledir/bin/maxscale -lstdout -df $maxscaledir/maxscale_secondary.cnf >& $maxscaledir/maxscale2.output &
+
+# Wait for the second MaxScale to start
+for ((i=0;i<60;i++))
+do
+    $maxscaledir/bin/maxadmin -S /tmp/maxadmin2.sock help >& /dev/null && break
+    sleep 0.1
+done
+
+# Give MaxScale some time to settle
+sleep 1