add a sleep when trying to destroy a vm
only start a session if a server exists
only destroy a session or server if they exist
add an updated duplicate VM check

if a duplicate vm is detected then it is destroyed before we boot a new VM.
change prepare method to be in line with sauce labs adapter
remove all duplicate servers, as there may be many
refactor(blue-box): extract finding duplicate servers
some more regex cleanup
Merge branch 'features/duplicate_and_template_handling' of github.com:travis-ci/travis-worker into features/duplicate_and_template_handling

merge in some awesomeness from Henrik

Conflicts:
	lib/travis/worker/virtual_machine/blue_box.rb
catch errors when trying to retrieve the server list from bluebox
Merge pull request #86 from travis-ci/features/duplicate_and_template_handling

Duplicate and template handling