client: move clean CCACHE to module
According 04b8575c52410bb6d31e0e55f1cf431d7cc9c7c3 cleaning CCACHE is
needed after installation. This commit moves this cleanup from
ipa-client-install to client.install() function
https://fedorahosted.org/freeipa/ticket/6392
Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>