build/packages/yum: fail if a package is missing

YUM does not fail if a package is missing in the list that we give to
the install function.
That means we have to detect when having a missing package and fail to
build the role.

Signed-off-by: Emilien Macchi <emilien.macchi@enovance.com>
Merge pull request #108 from enovance/check-pkg

build/packages/yum: fail if a package is missing