query_distro() will return version of package in proposed

When querying for a distro packages' version, the version of that package in -proposed will be returned if it differs from that in -release. This is problematic when trying to generate a list ofoutdated cloud archive packages.

Eg, currently saucy websockify -release version is 0.3.0-0ubuntu1. -proposed is 0.3.0+dfsg1-6.

>>> from cloudarchive import utils
>>> print utils.query_distro(package='spice-html5', release='saucy')
0~0+20130318+ec9ae0cbd6-2
>>> print utils.query_distro(package='websockify', release='saucy')
0.3.0+dfsg1-6

Should either take a parameter to specify which pocket to query, or only return versions from $series-release pocket