Do not pass client_name option to PluginClient constructor

[fbourigault]

Q	A
Bug fix?	yes
New feature?	no
BC breaks?	no
Deprecations?	no
Related tickets	fixup #71
Documentation	n/a
License	MIT

In #71, I missed to remove the client_name option from the options array before using it as PluginClient constructor third argument.

Before choosing to use unset, I was thinking to add the client_name option to PluginClient, use the OptionsResolver to set a default client name and add a getter to retrieve the client name. I don't choosed this way to not change anything in PluginClient, but if you find this solution better than the unset one, I would be happy to update this PR.

[Nyholm]

Why do we need to remove it?

[fbourigault]

To avoid the following exception:
Symfony\Component\OptionsResolver\Exception\UndefinedOptionsException: The option "client_name" does not exist. Defined options are: "debug_plugins", "max_restarts".

[Nyholm]

Oh, I thought the option resolver nicely ignored that...

Thank you.

[fbourigault]

Thank you for merging!