Use binary client for Set / UnsetAttr

[jessegeens]

EOS < 5.3 has a couple of bugs related to attributes:

• Attributes can only be removed as root or the owner, but over gRPC we cannot become root
• The recursive property is ignored on set attributes over gRPC

We circumvent these two issues by calling the binary client until we have deployed EOS 5.3\

That means that this PR has to be reverted once EOS 5.3 is live

[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]

This is ugly, as discussed, but we need it. At this point I'd add the same for the SetAttr, so that we fix the other issue with recursivity, and once we deploy EOS 5.3 this whole PR can be reverted.