One more offline+shutdown fix

Currently gnt-instance shutdown --force of an offline instance
resets the offline status. Which of course is bad and completely
unintended. Fix. (caught by the new qa tests)

Signed-off-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>

lib/cmdlib.py

@@ -7177,7 +7177,9 @@ class LUInstanceShutdown(LogicalUnit):
     node_current = instance.primary_node
     timeout = self.op.timeout
-    if not self.op.no_remember:
+    # If the instance is offline we shouldn't mark it as down, as that
+    # resets the offline flag.
+    if not self.op.no_remember and instance.admin_state in INSTANCE_ONLINE:
       self.cfg.MarkInstanceDown(instance.name)
     if self.primary_offline: