Description of problem:
Unfriendly expeption is shown as below if using "rhc app --help" or "rhc app create --help" while the libra server is not avaiable in express.conf.
# rhc app --help
Obtaining list of cartridges (please excuse the delay)...
/usr/share/ruby/net/http.rb:762:in `initialize': Connection refused - connect(2) (Errno::ECONNREFUSED)
    from /usr/share/ruby/net/http.rb:762:in `open'
    from /usr/share/ruby/net/http.rb:762:in `block in connect'
    from /usr/share/ruby/timeout.rb:68:in `timeout'
    from /usr/share/ruby/timeout.rb:99:in `timeout'
    from /usr/share/ruby/net/http.rb:762:in `connect'
    from /usr/share/ruby/net/http.rb:755:in `do_start'
    from /usr/share/ruby/net/http.rb:744:in `start'
    from /usr/local/share/gems/gems/rhc-0.99.2/lib/rhc-common.rb:376:in `http_post'
    from /usr/local/share/gems/gems/rhc-0.99.2/lib/rhc-common.rb:120:in `get_cartridges_list'
    from /usr/local/share/gems/gems/rhc-0.99.2/lib/rhc-common.rb:144:in `get_cartridge_listing'
    from /usr/local/share/gems/gems/rhc-0.99.2/bin/rhc-app:16:in `p_usage'
    from /usr/local/share/gems/gems/rhc-0.99.2/bin/rhc-app:500:in `<top (required)>'
    from /usr/local/bin/rhc-app:23:in `load'
    from /usr/local/bin/rhc-app:23:in `<main>'

Version-Release number of selected component (if applicable):
rhc-0.99.2.gem 

How reproducible:
always

Steps to Reproduce:
1. Keep an expired instance in ～/.openshift/express.conf like "ec2-184-72-194-136.compute-1.amazonaws.com"
2. Run "rhc app --help" or "rhc app create --help"
  
Actual results:
Exception is shown.

Expected results:
Help contents are shown correctly without error.

Additional info:
Other rhc commands can work fine.