Respect download.scheme in clone links

Gitblit-plugin did not respect gerrit.config's download.scheme
settings when passing web.otherUrls to Gitblit.  This change
attempts to evaluate download.scheme when populating
web.otherUrls. This is only interpretting download.scheme
when it is: not provided, http, or ssh.

Change-Id: Ife13c7a93aa8e1848a08429555ae1f61c0479895