Fixed issues related to OOIION-1276, particle-to-granule timestamping
Merge remote-tracking branch 'upstream/master'
Merge pull request #1316 from sfoley/master

Fixes for OOIION-1276, dataset agent timestamp issues

These tests pass prior to merge:

UNIT
SMOKE
ion/agents/instrument/test/test_instrument_agent.py
ion/agents/instrument/test/test_agent_connection_failures.py:TestAgentConnectionFailures
ion/agents/instrument/test/test_agent_persistence.py:TestAgentPersistence
ion/agents/instrument/test/test_agent_comms_alerts.py