Change async checkout behavior to be more like sync checkout: only create resources (connections) when they are needed.

    Now, connections should only be created on demand. The initial code created connections until the max limit of the pool was

    Some minor tweaks to test that confirm the desired behavior at a unit test level.
Changed reset and destroyRequestQueue to avoid any heavy weight synchronization methods. This should fix deadlock issue.
Remove an unnecessary synchronization primitive from keyedresourcepool.
Fixed Histogram: halved memory footprint, test boundary conditions, dropped unnecessary binary search.

These changes preserve/correct behavior of the current Histogram.

src/java/voldemort/store/stats/Histogram.java
- Halved memory footprint by dropping unnecessary "bounds" array
- Dropped unnecessary binary search, making insert O(1) rather than O(log(nBuckets))
- Improved documentation
- Made interface consistent for type of values inserted/got from histogram (i.e., all are 'long')

test/unit/voldemort/store/stats/HistogramTest.java
- Added tests for boundary conditions: -ive values are dropped on
  insert, "too large" values are bucketed in the final bucket on
  insert.

Minor fixes to RequestCounter calls to histogram to conform to 'long' interfaces.
Added INFO level messages to better understand statistics tracking (StoreStats, SocketClientStats, Histogram) behavior. Expect to remove most of these messages after debugging.

src/java/voldemort/store/stats/Histogram.java
- one more check to harden the imnplementation of insert

src/java/voldemort/store/stats/RequestCounter.java
- durationMs from int to long
- print out timing of histogram reset (q95, q99, reset)
Added INFO level messages to better understand connection creation. Expet to remove most of this after debugging.

src/java/voldemort/store/socket/clientrequest/ClientRequestExecutorFactory.java
- print out time to establish connection (if it takes longer than 1 ms)

src/java/voldemort/utils/pool/KeyedResourcePool.java
- print out info about object creation (connection establishment). In
  particular, how many outstanding creations (connection
  establishments) are in flight and how many idle resources are in the
  pool after the newly created resource is checked in.
Added INFO level messages to better understand resetting stats in ClientSocketStats. Expect to remove this after debugging.
Reverting minor-minor version change in build.properties.
Minor tweak to reduce INFO logging for KeyedResourcePool::attemptGrow
Added INFO level messages to better understand the performance of per-request instrumentation. Expect to remove most of this after debugging.
Clean up INFO debugging messages to be DEBUG. Minor other clean up too.
Change monitoring interval in ClientSocketStats to have larger window.
Minor code clean up based on review feedback

Protected all logger.(debug|info) statements I added with an is(Debug|Info)Enabled() check.

Made AsyncRecoveryFailureDetector less verbose. When it polls a server to see if it is available, it now prints out a clean INFO level message. It had been printing out a WARN level message *with* a stacktrace that made this expected behavior look much scarier than it really is.
Less verbose logging in the face of expected exceptions and error logging in the face of a slop not being written.

src/java/voldemort/cluster/failuredetector/AbstractFailureDetector.java
- less verbose logging when a node is unavailable

src/java/voldemort/store/routed/action/AbstractAction.java
- less verbose logging in the face of expected "exceptional" responses.

src/java/voldemort/store/slop/HintedHandoff.java
- ensure that an error message is logged if a slop is not written (we can grep for "Slop write of key.*was not written" in logs)
- added TODO because ObsoleteVersionExceptiosn are neither treated as failures or successes in the callback to sendHintParallel.

test/integration/voldemort/nonblocking/E2ENonblockingCheckoutTest.java
- minor fix

test/unit/voldemort/server/socket/ClientRequestExecutorPoolTest.java
- from junit3 to junit4
Reduce granularity of failure detector locking and do not destroy all enqueued requests upon setUnavailable.

src/java/voldemort/cluster/failuredetector/ThresholdFailureDetector.java
- Reduce amount of work done within synchronized section to reduce lock granularity and so ensure "side effects" of node being marked (un)available are not w/in sync section.

src/java/voldemort/store/socket/clientrequest/ClientRequestExecutorPool.java
- Added TODO/comment to decide whether we want to actively destroy all connections upon node being marked unavailable
- Switched behavior to lazily destroying connections.
Refactor all PerformParallel*Request classes.

- got rid of anonymous call back classes
- factored out waitForResponses logic and processResponses logic for most of these classes. GetAll stands out as being fairly different from the others.
- did not refactor to the point of sharing common code across classes, just refactored within each class.
- added many TODOs to the code for further refactoring.
Interim checkin with an ugly example of how threads could be created to handle callback work. The ugly code is commented out.
Added stress test and cleaned up client request executor pool reset.

reset(dest)
- changed behavior to match original KeyedResourcePool implementation. The original QueuedKeyedResourcePool.reset() was an unnecessary/bad behavior change that canceled enqueued requests. The original behavior was to destroy idle resources whenever pool is reset.

test/integration/voldemort/socketpool/E2EClientRequestExecutorPoolAndFailureDetectorTest.java
- stress test that has put and get threads contend for slow servers in such a manner as to trigger failure detection to mark nodes unavailable. This excercises connection tear down, reset(), and build up again. This also exercises the code paths in which callbacks do heavyweight work.
Clean up of TODOs and cruft code that had been introduced.
Fix for possible race condition for resource creation in KeyedResourcePool

See also http://code.google.com/p/project-voldemort/issues/detail?id=276