Take care of 'delete_failed' status from Heat

When deleting a Heat stack, solum only checks if the stack is gone. The 'delete_failed' status needs to be taken care of in the case of deletion errors from Heat.

https://github.com/stackforge/solum/blob/master/solum/deployer/handlers/heat.py#L165

Also there are a couple of places in solum deployer code where solum checks heat stack status in a loop with a growth_factor, which may potentially cause the loop takes a long time to finish. A better way might be to use a fixed timeout value for those checking loops.