ENG-6301 fix undo with prior duplicate rows inserted.
Merge branch 'master' into ENG-6301-bulk-loader-crash
ENG-6301 add ee test for undo of inserted duplicates
For ENG-6333, first version of latency watchdog.
For ENG-6333, use java thread instead of voltDB scheduleWork thread,
insert latency inspection points in network threads and ExecutionEngine
thread.
For ENG-6333, 2nd version of latency watchdog.
For ENG-6333, add logging rate limiter in latency watchdog.
For ENG-6333, change latency spike monitor points to see if latency
watchdog works.
For ENG-6333, add more latency spike inspection points.
For ENG-6333, replace System.out.println with VoltLogger.
For ENG-6333, run() method of latency watchdog should be sychronized.
For ENG-6333, use ConcurrentHashMap instead of HashMap.
performance charts: a few improvements for moving averages
ENG-6300 use persistent sequential nodes for truncation snapshot requests
For ENG-6333, use linked hash map to record timestamp per thread.
Merge pull request #1361 from VoltDB/ENG-6301-bulk-loader-crash

Eng 6301 bulk loader crash
ENG-6036 timestamp value as strings
Merge pull request #1374 from VoltDB/ENG-6300-II

ENG-6300 use persistent sequential nodes for truncation snapshot requests
For ENG-6333, remove debug code.
generate sql once