heat templates : fix IHA HeartbeatFailureAlarm during instance build

The HeartbeatFailureAlarm triggers prematurely while the instance is
building, because cfn-init doesn't create the files (hence the
heartbeat cron-job) until after the packges are all installed.
If we make the HeartbeatFailureAlarm depend on the WaitCondition, it
won't be created until the instance is fully built.

fixes bug 1100719

Change-Id: Iae73aa0974a3061f56aa3ee52598687f32c0f19b
Signed-off-by: Steven Hardy <shardy@redhat.com>