gitweb: Always use git-peek-remote in git_get_references

gitweb: Always use git-peek-remote in git_get_references

Instead of trying to read info/refs file, which might not be present
(we did fallback to git-ls-remote), always use git-peek-remote in
git_get_references.

It is preparation for git_get_refs_info to also return references
info.  We should not use info/refs for git_get_refs_info as the
repository is not served for http-fetch clients.

Signed-off-by: Jakub Narebski <redacted>
Signed-off-by: Junio C Hamano <redacted>