docs/reference/config: Fix galeb/vulcand links
docs/reference/config: Fix galeb/vulcand links

RsT doesn't support code formatting inside hyperlinks:

http://docutils.sourceforge.net/FAQ.html#is-nested-inline-markup-possible

Fix the rendering by making the link a separate reference. Keeping the
formatting means that it's easy to see the possible values.

tsuru/tsuru,ggarnier/tsuru,firebitsbr/tsuru,Endika/tsuru,gwmoura/tsuru,Endika/tsuru,guilhermebr/tsuru,hcxiong/tsuru,jblancett/tsuru,RichardKnop/tsuru,gciotta/tsuru,jblancett/tsuru,gciotta/tsuru,mderaldo/tsuru,gwmoura/tsuru,firebitsbr/tsuru,cezarsa/tsuru,ggarnier/tsuru,ggarnier/tsuru,tsuru/tsuru,mderaldo/tsuru,kgrvamsi/tsuru,tuxmonteiro/tsuru,guilhermebr/tsuru,ArxdSilva/tsuru,cezarsa/tsuru,gwmoura/tsuru,4eek/tsuru,cezarsa/tsuru,ArxdSilva/tsuru,gciotta/tsuru,tuxmonteiro/tsuru,4eek/tsuru,guilhermebr/tsuru,ArxdSilva/tsuru,firebitsbr/tsuru,RichardKnop/tsuru,tsuru/tsuru,Endika/tsuru,guilhermebr/tsuru,cgvarela/tsuru,mderaldo/tsuru,cgvarela/tsuru,jblancett/tsuru,hcxiong/tsuru,kgrvamsi/tsuru,hcxiong/tsuru,cezarsa/tsuru,tsuru/tsuru,kgrvamsi/tsuru,RichardKnop/tsuru,ggarnier/tsuru,ArxdSilva/tsuru,4eek/tsuru,cgvarela/tsuru,tuxmonteiro/tsuru