Native WaitConditionHandle move to common curl_cli

Move to a common curl_cli attribute, which can be used for both
success (default) and failure (by passing appropriate status data,
and optionally reason).  This should allow a slightly more flexible
interface than the current success/failure attributes, while still
remaining simple, and enabling simpler portability between this and
the alternative Swift signal implementation.

Note this breaks compatibility with the attributes we just recently
merged, but I'm assuming since it's so recent nobody is using it yet.

The example template at https://review.openstack.org/#/c/106424/ has
been updated to reflect the new interface.

Change-Id: Iac09aaa60ef5c1de27c9eeca7c65eca41c06907e
blueprint: native-waitcondition
Merge "Native WaitConditionHandle move to common curl_cli"