Make possible to get credentials value, since it's needed to start a console connection
Clean up Excon::Errors::SocketError::EOFError warning in vcloud_directory

Every time I make a connection with the vcloud_director provider I get this warning:

/Users/mray/.chgems/vchs/.gem/ruby/2.1.2/gems/fog-1.23.0/lib/fog/vcloud_director/compute.rb:372: warning: toplevel constant EOFError referenced by Excon::Errors::SocketError::EOFError
Merge pull request #3072 from mattray/vcloud_director_eoferror

Clean up Excon::Errors::SocketError::EOFError warning in vcloud_director
Merge pull request #2946 from fmbiete/xenserver_credentials

XenServer - attr_reader for Compute > connection > credentials