GUI-1148: Fix broken/missing Cancel links on launch config and launch instance wizards

Fixes the following for https://eucalyptus.atlassian.net/browse/GUI-1148
- Add "Cancel" link to each step of launch config wizard.
- Allow "Cancel" link on launch instance wizard to return to instances page.  
- Fix "Cancel" link in launch config wizard to go to the launch configs page rather than the instances page.