blockdevicemapping parsing bug in startElement.

[tosildaon]

In boto 2.38.0, I think there is a bug on startElement of blockdevicemapping.

I am trying to get existing launch configuration and create new launch configuration using it.
Here is a part of my code.

>>> conn = autoscale.connect_to_region(use_block_device_types=True)
>>> asg = conn.get_all_groups(names=["test-asg"])[0]
>>> lc = conn.get_all_launch_configurations(names=[asg.launch_config_name])[0]
>>> print lc.block_device_mappings
{u'/dev/sdd': <boto.ec2.blockdevicemapping.BlockDeviceType object at 0x20f9850>, u'/dev/sde': None, u'/dev/sdb': <boto.ec2.blockdevicemapping.BlockDeviceType object at 0x20f9850>, u'/dev/sdc': None, u'/dev/sda1': <boto.ec2.blockdevicemapping.BlockDeviceType object at 0x20f9850>}

There are three duplicated block device object mapped to different block device name. That is the bug.
Here is returned https response from AWS.

        <BlockDeviceMappings>
          <member>
            <NoDevice>true</NoDevice>
            <DeviceName>/dev/sdc</DeviceName>
          </member>
          <member>
            <NoDevice>true</NoDevice>
            <DeviceName>/dev/sde</DeviceName>
          </member>
          <member>
            <DeviceName>/dev/sda1</DeviceName>
            <Ebs>
              <VolumeType>standard</VolumeType>
              <DeleteOnTermination>true</DeleteOnTermination>
              <VolumeSize>20</VolumeSize>
            </Ebs>
          </member>
          <member>
            <NoDevice>true</NoDevice>
            <DeviceName>/dev/sdb</DeviceName>
          </member>
          <member>
            <NoDevice>true</NoDevice>
            <DeviceName>/dev/sdd</DeviceName>
          </member>
        </BlockDeviceMappings>

AWS returns correct information as I set on the AWS console, so bug is from parsing response in boto.

https://github.com/boto/boto/blob/2.38.0/boto/ec2/blockdevicemapping.py#L112-L116
I think above method should initialize self.current_value to None if name is not in ("ebs", "virtualname"). Shouldn't it?

Another thing.
LaunchConfiguration returned by get_all_launch_configurations has just BDM for block_device_mappings.
(https://github.com/boto/boto/blob/2.38.0/boto/ec2/autoscale/launchconfig.py#L214)
But To create LaunchConfiguration, I have to set list of BDM to block_device_mappings.
How about changing it to just BDM object, not list of BDM?