Fix potential deadlock in vnc_openstack

under certain circumstances (that alway happen in
contrail-installer + devstack environnement) keystoneclient
may authenticate before endpoints are populated in keystone.
In that case, It'll be usable to list projects, but not to
read them. Thus, it won't be reset by resync_all_projects,
but neutron api will stay stuck as projects can't be added
to vnc.

Closes-bug: #1384265
Change-Id: Iefd107604ae9f16a2b91d74c188781ef1a52394f
Merge "Fix potential deadlock in vnc_openstack"