Schema not validating with connector `configfilesection` property

[pkaczynski]

There is a bug in serializing connector properties when using configfilesection. Example:

request_source = esp.SourceWindow(
    name='request',

    schema=('espid*:int64', 'clnt_id:double'),
    index_type='empty', insert_only=True,
)
request_source.add_connector(
    SocketPublisher(configfilesection='[REQS]')
)

In the end it gives xml like this:

<connectors>
    <connector class="fs" name="c_w5y9lijs" type="publish">
    <properties>
        <property name="configfilesection">[REQS]</property>
        </properties>
        <properties/>
    </connector>
</connectors>

The <properties/> is too much and chema does not validate giving an error

SPError: load project failed: DataOpsPython, /tmp/fileTwmtwN:28:28: error: element "properties" not allowed here; expected the element end-tag

Uploading this project from this xml, however, gives no errors.