domain: features: treat <vmcoreinfo/> as a tristate

When it was initially introduced, vmcoreinfo was a boolean option,
but that was changed a release latest to be a tristate.

tests/cli-test-xml/compare/virt-install-singleton-config-2.xml

@@ -88,7 +88,7 @@
       <synic state="on"/>
     </hyperv>
     <vmport state="off"/>
-    <vmcoreinfo/>
+    <vmcoreinfo state="on"/>
   </features>
   <cpu mode="custom" match="strict">
     <model>foobar</model>
@@ -283,7 +283,7 @@
       <synic state="on"/>
     </hyperv>
     <vmport state="off"/>
-    <vmcoreinfo/>
+    <vmcoreinfo state="on"/>
   </features>
   <cpu mode="custom" match="strict">
     <model>foobar</model>

tests/xmlparse-xml/change-guest-out.xml

@@ -27,7 +27,7 @@
     </hyperv>
     <vmport state="on"/>
     <viridian/>
-    <vmcoreinfo/>
+    <vmcoreinfo state="on"/>
     <kvm>
       <hidden state="on"/>
     </kvm>

tests/xmlparse.py

@@ -177,7 +177,7 @@ class XMLParseTest(unittest.TestCase):
         check("hyperv_spinlocks", True, True)
         check("hyperv_spinlocks_retries", 12287, 54321)
         check("vmport", False, True)
-        check("vmcoreinfo", False, True)
+        check("vmcoreinfo", None, True)
         check("kvm_hidden", None, True)
         check("pvspinlock", None, True)
         check("gic_version", None, False)

virtinst/domain/features.py

@@ -39,7 +39,7 @@ class DomainFeatures(XMLBuilder):
     pvspinlock = XMLProperty("./pvspinlock/@state", is_onoff=True)
 
     smm = XMLProperty("./smm/@state", is_onoff=True)
-    vmcoreinfo = XMLProperty("./vmcoreinfo", is_bool=True)
+    vmcoreinfo = XMLProperty("./vmcoreinfo/@state", is_onoff=True)
 
 
     ##################