bionic-amd64-tf-a-build: add 'util-linux' package

Updated dockerfile to install 'util-linux' package, needed
by FVP CI scripts to execute 'uuidgen' command.

Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
Change-Id: I066fab1fafaefd1998c260a03c90b8f8ed5eb9d2
1 file changed