Adds exception handling to heat code

Reasons:
- In absence of exception handling code, instance status used to be
  always in BUILD state, even if heat code has error'd out.
- status "CREATE_FAILED" of heat stack should also be candidate
  of code failure and instead of executing next code,
  exception should be raised for this status.
- Resource state should also be verified before keeping their IDs.

Changes:
- Exception handling code added, which would set instance status
  to ERROR for any failures.
- Added HEAT_STACK_SUCCESSFUL_STATUSES & HEAT_RESOURCE_SUCCESSFUL_STATES
- Heat Stack status is verified with HEAT_STACK_SUCCESSFUL_STATUSES,
  and raises exception on failure.
- Heat Resource state is verified with HEAT_RESOURCE_SUCCESSFUL_STATES,
  and raises exception on failure.

Change-Id: I307d3d6bbdcd9a46b6ea94e9673ee8d1d97e50bd
Closes-Bug: #1263496