Support GCE instances with no service accounts
This fixes  When an empty list (`[]`) is passed in for ex_service_accounts,
a VM with no service accounts is created.  When None is passed in (the default),
the behavior remains unchanged, giving the default service account.
@@ -4893,7 +4893,7 @@ class GCENodeDriver(NodeDriver):
:rtype: ``list`` of ``dict``
"""
gce_service_accounts = []
- if not service_accounts:
+ if service_accounts is None:
gce_service_accounts = [{
'email': default_email,
'scopes': [self.AUTH_URL + default_scope]
