Fixing broken links

1. Dead link to the HA guide. Added a comment regarding
availability and reliability.
2. Hyper-v link re-routed to Azure instead of Hyper-V.
Updated this so it reflects Hyper-V docs.

Suggestion: Might be worth mentioning which Hyper-V servers
ceilometer actually supports.

Change-Id: I4a56ee26ae39ab02bed8bac8d0e364322617622c
backport: stein rocky

doc/source/admin/telemetry-best-practices.rst

@@ -26,4 +26,9 @@ Data collection
 #. If polling many resources or at a high frequency, you can add additional
    central and compute agents as necessary. The agents are designed to scale
    horizontally. For more information refer to the `high availability guide
-   <https://docs.openstack.org/ha-guide/controller-ha-telemetry.html>`_.
+   <https://docs.openstack.org/ha-guide/>`_.
+
+   .. note::
+
+      The High Availability Guide is a work in progress and is changing
+      rapidly while testing continues.

doc/source/admin/telemetry-system-architecture.rst

@@ -79,7 +79,7 @@ compute hosts.
 The following is a list of supported hypervisors.
 
 -  `Libvirt supported hypervisors <http://libvirt.org/>`__ such as KVM and QEMU
--  `Hyper-V <http://www.microsoft.com/en-us/server-cloud/hyper-v-server/default.aspx>`__
+-  `Hyper-V <https://docs.microsoft.com/en-us/windows-server/virtualization/hyper-v/hyper-v-on-windows-server>`__
 -  `XEN <http://www.xenproject.org/help/documentation.html>`__
 -  `VMware vSphere <https://www.vmware.com/support/vsphere-hypervisor.html>`__