dcap: Fix regression in published protocol family

Prior to 2.7, gsidcap was published as gsidcap and the SRM used this
as the protocol name when negotiating the transfer protocol. 2.7
always publishes 'dcap', which is a regression compared to 2.6.

This patch resolves the problem.

Target: trunk
Request: 2.11
Request: 2.10
Request: 2.9
Request: 2.8
Request: 2.7
Require-notes: yes
Require-book: no
Reported-by: Yvan Calas <yvan.calas@cc.in2p3.fr>
Acked-by: Paul Millar <paul.millar@desy.de>
Patch: https://rb.dcache.org/r/7587/
(cherry picked from commit f0d4e8f53ef87dc26f895c74b8a9eb89f585dfa2)