Recovered DFO logs cause collector Sink to exit with error.

An event that is saved using the disk failover path adds a rolltag field.

When this entry is recovered, it fails when delivered to a collector sink because it tries to overwrite the rolltag field.

How to duplicate:

First setup, setup agent with no collector up.
node : console | agentDFOSink;

Add some entries.

Then setup a collector
collector: collectorSource | collectorSink("file:///tmp/foo","bar");

Collector eventually enters error state.