Unable to find gitolite version when PTY allocation is denied

The defaut gitolite behaviour is to set authorized keys with "no-pty"
option.

Trying an SSH connection without a command execute a login shell which
output "Pseudo-terminal will not be allocated because stdin is not a
terminal" error message in addition to the result of the "info" command.

* lib/libs/git_hosting.rb (GitHosting.gitolite_version): run the "info"
  command explicitly.

* lib/libs/git_hosting.rb (GitHosting.gitolite_version_output): Ditoo.