Use explicit object locks for reads and writes instead of syncrhonized methods for databaseLazyLoad and databaseLazyWrite
Kickoff meta batch timers only if batch mode is enabled
Check the actual FIFO queue for meta writes is not empty before writing
getIfPresent() should be called on CompoundKey before writing meta to disk
Add instrumentation around scanMetrics and checkMeta
Merge pull request #304 from lakshmi-kannan/bf_fix_class_cast

Bunch of bug fixes to the MetadataCache batched reads and writes.