add user to virt role

defaults/main.yml

@@ -1,2 +1,3 @@
 ---
-# defaults file for vmserver
+# defaults file for vmserver
+virt_default_user: root

templates/qemu.conf.j2

@@ -445,7 +445,7 @@
 #       user = "+0"     # Super user (uid=0)
 #       user = "100"    # A user named "100" or a user with uid=100
 #
-#user = "root"
+user = {{virt_default_user}}
 
 # The group for QEMU processes run by the system instance. It can be
 # specified in a similar way to user.