Improve gitaly_address error message
Improve gitaly_address error message

Closes gitaly#174

dreampet/gitlab,jirutka/gitlabhq,stoplightio/gitlabhq,axilleas/gitlabhq,mmkassem/gitlabhq,dplarson/gitlabhq,mmkassem/gitlabhq,iiet/iiet-git,dplarson/gitlabhq,t-zuehlsdorff/gitlabhq,jirutka/gitlabhq,dreampet/gitlab,htve/GitlabForChinese,dreampet/gitlab,dreampet/gitlab,darkrasid/gitlabhq,htve/GitlabForChinese,mmkassem/gitlabhq,htve/GitlabForChinese,htve/GitlabForChinese,stoplightio/gitlabhq,mmkassem/gitlabhq,jirutka/gitlabhq,dplarson/gitlabhq,iiet/iiet-git,dplarson/gitlabhq,iiet/iiet-git,jirutka/gitlabhq,darkrasid/gitlabhq,darkrasid/gitlabhq,stoplightio/gitlabhq,stoplightio/gitlabhq,t-zuehlsdorff/gitlabhq,axilleas/gitlabhq,axilleas/gitlabhq,t-zuehlsdorff/gitlabhq,darkrasid/gitlabhq,iiet/iiet-git,t-zuehlsdorff/gitlabhq,axilleas/gitlabhq