heat templates : add missing credentials to IHA template

WordPress_Single_Instance_With_IHA lacks credentials so
cfn-push-stats can't authenticate with the cloudwatch api

ref bug 1100719

Change-Id: I218eea927a00b6cef58a4a1ee5d930c57ebb8a2e
Signed-off-by: Steven Hardy <shardy@redhat.com>
heat templates : IHA HeartbeatFailureAlarm should be Ref

cfn-push-stats reference to HeartbeatFailureAlarm should be a
Ref not a hard-coded string, or the engine fails to find the
watch because the name lacks the stack prefix

ref bug 1100719

Change-Id: I0fbec026b883348b674327ae6e097a9452ce375f
Signed-off-by: Steven Hardy <shardy@redhat.com>