Catch unhandled exception and prints contribution message

Fix #115
Handle global exception in abstract_command
add the same behaviour in abstract action than in abstract command
fix merge errors
Remove redondant rubocop:disable
Make WaitForServerToBeAccessible inherits from AbstractAction
Known errors must not be caught
Introduce Errors::Timeout

Now it is important that all expected exceptions
inherit from VagrantOpenstackError
Merge pull request #117 from ggiamarchi/catch_ex

Catch unhandled exception and prints contribution message