roles/homeassistant: Install in a virtualenv

Because the Home Assistant user's home directory is on `/var`, Python
packages installed in the "user site" do not get the correct SELinux
labels and thus run in the wrong domain.  This causes a lot of AVC
denials and other issues that prevent Home Assistant from working
correctly.

To resolve this issue, Home Assistant is now installed in a virtual
environment at `/usr/local/homeassistant`.  This directory is still
owned by the Home Assistant user, allowing Home Assistant to manage
packages installed there.  Since it is rooted under `/usr`, files are
labelled correctly and processes launched from executables there will
run in the correct domain.

roles/homeassistant/handlers/main.yml

@@ -1,3 +1,5 @@
+- name: relabel home assistant dir
+  command: restorecon -RF /usr/local/homeassistant
 - name: reload systemd
   command: systemctl daemon-reload
 - name: restart homeassistant