doc: allow_resize_to_same_host needs nova-api restarted

[DEFAULT]allow_resize_to_same host is a bit weird. It controls
scheduling, is set in the [DEFAULT] section, but needs nova-api to be
restarted for changes to take effect (the API layer calls
compute_api.resize(), and the allow_resize_to_same_host check is
performed there, and not in the scheduler). This patch adds a small
blurn to the config help text to explain this.

Change-Id: I5393dfaeaf123d28bb1889635792ee1ece2c5295

Author: notartom

nova/conf/compute.py

@@ -51,7 +51,8 @@
 testing in single-host environments. By default it is not allowed
 to resize to the same host. Setting this option to true will add
 the same host to the destination options. Also set to true
-if you allow the ServerGroupAffinityFilter and need to resize.
+if you allow the ServerGroupAffinityFilter and need to resize. For changes to
+this option to take effect, the nova-api service needs to be restarted.
 """),
     cfg.ListOpt('non_inheritable_image_properties',
         default=['cache_in_nova', 'bittorrent'],