Improve Dockerfile.revad-eos

[ebocchi]

• Use EOS 4.8.91
• Bring back multi-stage build
• Copy the resulting revad from the builder container

Resulting image size (unpacked on disk) is 2.59GB

• eos-all:4.8.91 is 2.47GB
• existing revad:latest-eos is 6.18GB

[update-docs]

Thanks for opening this pull request! The maintainers of this repository would appreciate it if you would create a changelog item based on your changes.

[glpatcern]

Nice!

[jimil749]

/cc @SamuAlfageme can we get this merged, so that it can be used for Sciencebox?

[SamuAlfageme]

@ebocchi the CI was failing due to a missing x-ref to the GitHub PR

[glpatcern]

@ebocchi I'm sorry to have screwed part of this change :-P can you please rebase it on top of master ?

[ebocchi]

@glpatcern
Rebased against master. Should be good to go now ;)

[gmgigi96]

@ebocchi can you fix the linter (Codacy Static Code Analysis)?

[ebocchi]

As per @glpatcern, going back to eos-client-4.8.91-1.el7.cern.x86_64 as the only package needed is eos-client.
eos-client-4.8.91-1.el7.cern.x86_64 include:

# rpm -qa | grep ^eos | sort
eos-client-4.8.91-1.el7.cern.x86_64
eos-folly-2019.11.11.00-1.el7.cern.x86_64
eos-folly-deps-2019.11.11.00-1.el7.cern.x86_64
eos-fusex-4.8.91-1.el7.cern.x86_64
eos-fusex-core-4.8.91-1.el7.cern.x86_64
eos-fusex-selinux-4.8.91-1.el7.cern.x86_64
eos-protobuf3-3.5.1-5.el7.cern.eos.x86_64
eos-xrootd-4.12.8-1.el7.cern.x86_64