Fixed spelling error in Ceilometer

Change-Id: I814c25037fca6a71580bfa437cb918bb016f1c82
storage: store recording timestamp

This patch adds a record_at field in the sample that are stored that
indicates when the timestamp has been stored in the database.

Change-Id: Ia0ff8bd07fd811fe8d3050d30971a05a277798d0
Blueprint: storage-sample-timestamp
Merge "Fixed spelling error in Ceilometer"