Allow specification of domain shares (#925)

Weighted priority of the domain relative to others on the host.

spec/unit/templates/domain_all_settings.xml

@@ -14,6 +14,9 @@
   <numatune>
     <memory nodeset='1-4,^3,6'/>
   </numatune>
+  <cputune>
+    <shares>1024</shares>
+  </cputune>
 
   <os>
         <type arch='x86_64' machine='pc-compatible'>hvm</type>

spec/unit/templates/domain_spec.rb

@@ -76,6 +76,7 @@ describe 'templates/domain' do
 
       domain.qemuargs(value: '-device')
       domain.qemuargs(value: 'dummy-device')
+      domain.shares = '1024'
       domain.cpuset = '1-4,^3,6'
       domain.nodeset = '1-4,^3,6'
     end