Check if domain is running in qemuDomainAgentIsAvailable

If the domain is not running, the agent will not respond.
Do not even try.

https://bugzilla.redhat.com/show_bug.cgi?id=872424
(cherry picked from commit 72352232)

src/qemu/qemu_domain.c

@@ -2819,6 +2819,13 @@ qemuDomainAgentAvailable(virDomainObjPtr vm,
         }
         return false;
     }
+    if (virDomainObjGetState(vm, NULL) != VIR_DOMAIN_RUNNING) {
+        if (reportError) {
+            virReportError(VIR_ERR_OPERATION_INVALID, "%s",
+                           _("domain is not running"));
+        }
+        return false;
+    }
     return true;
 }