stack/caucase: Depend on monitor

Then using caucase implies monitor, and it's not required to do so in the
softwares using monitor.

software/caddy-frontend/software.cfg

@@ -16,8 +16,6 @@ extends =
   ../../component/nginx/buildout.cfg
 
   ../../stack/caucase/buildout.cfg
-# Monitoring stack (keep on bottom)
-  ../../stack/monitor/buildout.cfg
 
 parts +=
   caucase-eggs

software/caucase/software.cfg

@@ -2,8 +2,6 @@
 extends =
   buildout.hash.cfg
   ../../stack/caucase/buildout.cfg
-# Monitoring stack (keep on bottom)
-  ../../stack/monitor/buildout.cfg
 
 parts +=
   instance

stack/caucase/buildout.cfg

@@ -2,6 +2,7 @@
 extends =
   buildout.hash.cfg
   ../slapos.cfg
+  ../monitor/buildout.cfg
   ../../component/python-cryptography/buildout.cfg
 parts =
   slapos-cookbook