MXS-1027: Add Upstart config file

Various older systems use Upstart to control services. MaxScale should
provide both init.d scripts and Upstart configurations for systems that
don't support systemd.

etc/upstart/maxscale.conf.in

@@ -0,0 +1,26 @@
+# MaxScale service
+
+description "MariaDB MaxScale"
+
+start on stopped rc RUNLEVEL=[2345]
+stop on starting rc runlevel [!2345]
+
+# Respawn the process on abnormal exits
+respawn
+
+# Uncomment this to limit respawns to two every five minutes
+# respawn limit 2 5
+
+# Unlimited open files
+limit nofile unlimited unlimited
+
+# Make sure /var/run/maxscale exists
+pre-start exec /usr/bin/install -d -o maxscale -g maxscale @MAXSCALE_VARDIR@/run/maxscale
+
+# Change the user to maxscale:maxscale
+setuid maxscale
+setgid maxscale
+
+# Start MaxScale
+expect fork
+exec /usr/bin/maxscale