Install git for uscan in packaging-updates

For some packages, the watch file use the "git" mode to check git repository, in that case git is required otherwise it fails with:

uscan issue: Command 'git' not found in /usr/local/sbin, /usr/local/bin, /usr/sbin, /usr/bin, /sbin, /bin at /usr/share/perl5/Devscripts/Utils.pm line 24.

Signed-off-by: Dylan Aïssi dylan.aissi@collabora.com