fix OOIION-1372; includes new specific test

Fix https://jira.oceanobservatories.org/tasks/browse/OOIION-1372

(new PR because had some trouble with conflicts with the previous one).

test_resource_monitoring_recent is the specific test:

    bin/nosetests -sv --nologcapture ion/agents/platform/test/test_platform_agent_with_rsn.py:TestPlatformAgent.test_resource_monitoring_recent
    ...
    2013-12-05 08:30:11,056 INFO Dummy-7 ion.agents.platform.test.test_platform_agent_with_rsn:747 test_resource_monitoring_recent: using attr_id='input_bus_current': monitor_cycle_seconds=5
    2013-12-05 08:30:11,056 INFO Dummy-7 ion.agents.platform.test.test_platform_agent_with_rsn:753 test_resource_monitoring_recent: sleeping for 30 secs before resuming monitoring
    ...
    2013-12-05 08:30:41,057 INFO Dummy-7 ion.agents.platform.test.test_platform_agent_with_rsn:762 test_resource_monitoring_recent: re-starting monitoring
    ...
    2013-12-05 08:30:53,877 INFO Dummy-7 ion.agents.platform.test.test_platform_agent_with_rsn:785 test_resource_monitoring_recent: sample received, min_reported_time_millis=1386261044000
    
@MauriceManning please review