Fix indentation issue in wait_for_change override

The ovsdbapp.backend.ovs_idl.idlutils.wait_for_change method was
overriden in Ia9e23113fdeebf0b99085da200c3d61b71567d36. Unfortunately,
and indentation error was introduced which rendered the method as a
NoOp if a seqno was passed to it.

Closes-Bug: #1989646
Change-Id: I9d8db215ba19ea88bc615b7b30084113a3c953d4
(cherry picked from commit fb7d937)

Author: otherwiseguy

neutron/plugins/ml2/drivers/ovn/mech_driver/ovsdb/impl_idl_ovn.py

@@ -50,10 +50,10 @@
 def wait_for_change(idl_, timeout, seqno=None):
     if seqno is None:
         seqno = idl_.change_seqno
-        while idl_.change_seqno == seqno and not idl_.run():
-            poller = idlutils.poller.Poller()
-            idl_.wait(poller)
-            poller.block()
+    while idl_.change_seqno == seqno and not idl_.run():
+        poller = idlutils.poller.Poller()
+        idl_.wait(poller)
+        poller.block()
 
 
 idlutils.wait_for_change = wait_for_change