Add support for testing release builds

Add support for testing release builds

It turns out the only change needed is to introduce the
BUNDLE_URL variable which is supposed to hold the URL from
which the tested ODL distribution is downloaded.
The releng jobs shall use ACTUALBUNDLEURL environment
variable to fill this Robot variable. The code then gets the
URL, snips out everything starting from "org/opendaylight"
and uses the result as the base URL. This makes the "type"
argument of the deployment keyword unnecessary so it was
removed.

Change-Id: I7457b05af25a517d5cdc21011dbdae1e4b34be2a
Signed-off-by: Jozef Behran <jbehran@cisco.com>