Update image flavor to have some disk

It seems nova has changed defaults on who can create zero-sized
disk instances [1] and now os_tempest jobs failed with
Only volume-backed servers are allowed for flavors with zero disk.
Changing the disk to 1 fixes the same.

[1] https://review.openstack.org/#/c/603910/

Change-Id: Id7467d037a7b0b4cb46add587395b21f28fb9df7

config_tempest/flavors.py

@@ -56,7 +56,7 @@ class Flavors(object):
                 flavor_id = self.create_flavor(pref['name'], ram=pref['ram'])
                 self._conf.set('compute', pref['key'], flavor_id)
 
-    def create_flavor(self, flavor_name, ram=64, vcpus=1, disk=0):
+    def create_flavor(self, flavor_name, ram=64, vcpus=1, disk=1):
         """Create flavors or try to discover two smallest ones available.
 
         :param flavor_name: flavor name to be created (usually m1.nano or

roles/generate-tempestconf-file/tasks/test-demo-user.yaml

@@ -12,7 +12,7 @@
           --public \
           --ram {{ item.ram }} \
           --vcpus 1 \
-          --disk 0 \
+          --disk 1 \
           {{ item.name }}
     with_items:
       - { name: "m1.nano", ram: 64 }