New Build api exposed via 'beta' rather than 'devel'

This may be a lazr.restful issue but as per bug 588062 (comment 4), the new build API is exposed under "beta" rather than "devel" (the 1.0 API reflects the old api as expected). See the "date_finished" attribute at:

https://edge.launchpad.net/+apidoc/beta.html#build

versus:

https://edge.launchpad.net/+apidoc/devel.html#build

As an example, date_finished is exported as follows (in IBuildFarmJob):
{{{
    date_finished = exported(
        Datetime(
            title=_("Date finished"), required=False, readonly=True,
            description=_(
                "The timestamp when the build farm job was finished.")),
        ("1.0", dict(exported=True, exported_as="datebuilt")))
}}}

 - the assumption being that the default export would be devel.

The documentation actually checks (what it thought was) the devel version against the 1.0 version, but I guess the webservice in our test is also defaulting to beta.

lib/lp/soyuz/stories/webservice/xx-builds.txt