GSF.TimeSeries: Fixed race condition in MeasurementKey.
GSF.TimeSeries: Fixed race condition in MeasurementKey.

git-tfs-id: [https://tfs.codeplex.com/tfs/TFS07]$/gsf/Main;C94374

GridProtectionAlliance/gsf,GridProtectionAlliance/gsf,rmc00/gsf,GridProtectionAlliance/gsf,rmc00/gsf,rmc00/gsf,rmc00/gsf,GridProtectionAlliance/gsf,rmc00/gsf,GridProtectionAlliance/gsf,GridProtectionAlliance/gsf,rmc00/gsf,rmc00/gsf,GridProtectionAlliance/gsf,GridProtectionAlliance/gsf