Add note on systemvm upgrade changes

Author: Pearl1594

source/installguide/management-server/_systemvm.rst

@@ -16,6 +16,9 @@
 Prepare the System VM Template
 ------------------------------
 
+From Apache CloudStack v4.16 onwards, upgrade path handles systemVM template registration, if not done prior to initiating upgrade.
+One may choose, to also omit the systemVM template seeding step during fresh installation of CloudStack, as support has been added to 
+initiate systemVM template registration for all hypervisors present in the zone when the first secondary storage pool is added.
 Secondary storage must be seeded with a template that is used for
 CloudStack system VMs.
 

source/upgrading/index.rst

@@ -28,6 +28,12 @@ Upgrading CloudStack
 This document contains the instructions for upgrading CloudStack from prior releases, to the current 
 release.  Please read through all sections carefully before starting.
 
+For ACS 4.16 onwards, seeding of system-VM template is optional, as this will be taken care of by either the upgrade process or
+in case of a fresh deployment, registration of the systemVM template(s) is handled during the addition of the first image store to the zone.
+The `cloudstack-management` package will now include the systemVM templates for KVM, XenServer and VMWare. In case templates aren't already registered
+either prior upgrade or during fresh installation, ACS will handle the template registration automatically, by mounting the secondary store onto the 
+management server, copying the respective templates to the store and then creating the `template.properties` file.
+
 .. note::
    For information on the API changes and issues fixed in this release, please see the Release Notes section of the documentation
 

source/upgrading/upgrade/_sysvm_templates.rst

@@ -28,7 +28,10 @@ Update System-VM templates
 #. Click Register template.
    The Register template dialog box is displayed.
 
-#. In the Register template dialog box, specify the following values
+#. From ACS 4.16 onwards, CloudStack will support automatic registration of systemVM
+   templates, if not done prior initiating upgrade. However, the usual upgrade process 
+   continues to be supported. To register the system VM template do the following:
+   In the Register template dialog box, specify the following values
    (do not change these):
 
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