Force a reinstall of the protobuf gem

Fixes: https://gitlab.com/gitlab-org/omnibus-gitlab/issues/2042

The gem with precompiled extensions is known to not work on older gcc compiles Which ship in debian 7 and centos 6

We remove the bad gem, and install the new one, forcing it to compile on the current platform

It would be nicer if we could have set bundler to do this for us, but bundler runs a Best vs Worst case check for platform before installing, and will install the pre-built binary even if we have a gemfile that says to use ruby. (It considers the generic platforms to be worst case)