Run hooks even without cfn-init Metadata.

When we don't have AWS::CloudFormation::Init in Metadata, this just
means that cfn-init cannot do anything. However, cfn-hup still has hooks
which are just scheduled to be run on any change in the Metadata.

Fixes bug #1155999

Change-Id: I21c4f2137f8045128a86278b4d90768ea97455d1