offline upgrade 1.8.1->2.0.1: impossible to create RestConnection when some nodes are upgraded first: couchApiBase doesn't exist in nodes/self

build 164
run as a example:
http://qa.hq.northscale.net/job/ubuntu-64-2.0-upgrade/88/consoleFull
./testrunner -i /tmp/upgrade.ini upgrade_version=2.0.1-164-rel,initial_vbuckets=64,get-cbcollect-info=True -t newupgradetests.MultiNodesUpgradeTests.offline_cluster_upgrade,initial_version=1.8.1-942-rel,nodes_init=3,sasl_buckets=1,standard_buckets=1,GROUP=1_8;OFFLINE

steps:
1. 3 1.8.1-942 node in cluster
2. async upgrade all nodes
3. after upgrade we are tying to create rest connection:
request nodes/self to get couchApiBase but it is not there for a while

in test when we create RestConnection we use loop to get API for 2.* version if something is wrong

for iteration in xrange(5):
if "couchApiBase" not in http_res.keys():
if self.is_cluster_mixed():
self.capiBaseUrl = self.baseUrl + "/couchBase"
return
http_res, success = self.init_http_request(self.baseUrl + 'nodes/self')
else:
self.capiBaseUrl = http_res["couchApiBase"]
return

I tried to set 5 * 5 seconds but it does not help.

at the same time, the 'nodes/self' has couchApiBase after all servers were updated( checked it manually)

I believe that couchApiBase is not set until all the servers in the cluster will not come back after the upgrade