Add python-zaqarclient to global-requirements

After the rename, a new version of zaqarclient has been released. This
commit adds the library to the global-requirements but keeps the old
marconiclient, which would likely be used for stable branches. It'll
remove once it's completely obsolete.

Change-Id: I27d4ea6180e849e5098ece6f3ba580d422be38a2
Merge "Add python-zaqarclient to global-requirements"