Support provisioning flavors with no root disk

app/models/manageiq/providers/openstack/cloud_manager/provision/volume_attachment.rb

@@ -1,6 +1,6 @@
 module ManageIQ::Providers::Openstack::CloudManager::Provision::VolumeAttachment
   def create_requested_volumes(requested_volumes)
-    volumes_attrs_list = [default_volume_attributes]
+    volumes_attrs_list = instance_type.root_disk_size > 0 ? [default_volume_attributes] : []
 
     connection_options = {:service => "volume", :tenant_name => cloud_tenant.try(:name)}
     source.ext_management_system.with_provider_connection(connection_options) do |service|

spec/models/manageiq/providers/openstack/cloud_manager/provision/volume_attachment_spec.rb

@@ -34,6 +34,23 @@
 
       expect(@task.create_requested_volumes(@task.options[:volumes])).to eq [default_volume, requested_volume]
     end
+
+    context "with root volume" do
+      @flavor = FactoryBot.create(:flavor_openstack, :root_disk_size => 0)
+
+      it "creates a bootable first volume" do
+        service = double
+        allow(service).to receive_message_chain('volumes.create').and_return @volume
+        allow(@task.source.ext_management_system).to receive(:with_provider_connection)
+          .with({:service => 'volume', :tenant_name => nil}).and_yield(service)
+        allow(@task).to receive(:instance_type).and_return(@flavor)
+
+        requested_volume = {:name => "root", :size => 2, :uuid => @volume.id, :source_type => "volume",
+                            :destination_type => "volume"}
+
+        expect(@task.create_requested_volumes(@task.options[:volumes])).to eq [requested_volume]
+      end
+    end
   end
 
   context "#check_volumes" do