message sends from periodic calls attributed to previous entry

*Original author: Jim Phillips (@jcphill)*
*Original issue: https://charm.cs.illinois.edu/redmine/issues/699*

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When tracing messages back, any message generated by a non-entry such as a periodic callback triggers tracing back from the previous entry on that PE. Tracing should stop at the periodic call, or potentially trace back to the entry that created the periodic callback.