qemu: Make migration events mandatory

All QEMU versions we care about support migration events and we should
be able to enable the associated capability when connecting to the
monitor. Failure to do so is thus considered fatal now.

Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>

src/qemu/qemu_migration_params.c

@@ -1433,10 +1433,8 @@ qemuMigrationCapsCheck(virQEMUDriver *driver,
 
     qemuDomainObjExitMonitor(vm);
 
-    if (rc < 0) {
-        virResetLastError();
-        VIR_DEBUG("Cannot enable migration events");
-    }
+    if (rc < 0)
+        return -1;
 
     /* Migration events capability must always be enabled, clearing it from
      * migration capabilities bitmap makes sure it won't be touched anywhere