Add krb5 dependency for packaging
Created by: crohr
Update packager.io recipe to install libkrb5-dev
before the bundle install
step, otherwise the package fails to build on ubuntu 14.04.
Before: https://packager.io/gh/gitlabhq/gitlabhq/build_runs/142#10313 After: https://packager.io/gh/pkgr/gitlabhq/build_runs/42#10327