Force check remote updates when checking for new plugin versions

Force check remote updates when checking for new plugin versions

Without the -U option, the plugin versions could be cached from a
while ago. This partly explains why the Hudson build would not
display the new updates. (Also the proxy settings had to be fixed)

Change-Id: Ib17d14d058b5d8f1894c61448fd3192972630291
Signed-off-by: Marc-Andre Laperle <marc-andre.laperle@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/67721
Reviewed-by: Hudson CI
Reviewed-by: Alexandre Montplaisir <alexmonthy@efficios.com>