Update min supported service version for Zed

Nova only supports compute services that are not older than version
N-1. So in Zed the smallest supported nova compute version is Yoga
and the smallest Yoga service version is 61.

Change-Id: I4cbe233087577c7754856afcc4e3fe9fdc2d3008
Signed-off-by: Takashi Natsume <[email protected]>

Author: takanattie

nova/objects/service.py

@@ -230,11 +230,12 @@
 # This is used to raise an error at service startup if older than N-1 computes
 # are detected. Update this at the beginning of every release cycle to point to
 # the smallest service version that was added in N-1.
-OLDEST_SUPPORTED_SERVICE_VERSION = 'Xena'
+OLDEST_SUPPORTED_SERVICE_VERSION = 'Yoga'
 SERVICE_VERSION_ALIASES = {
     'Victoria': 52,
     'Wallaby': 54,
     'Xena': 57,
+    'Yoga': 61,
 }