CBST-16: improve exception handling in sdk

when bucket/node goes down, process should be notified and threads restarted.

Change-Id: I51d72e9ebf64815a6be715e63fc1baf5b641d123
Reviewed-on: http://review.couchbase.org/30534
Reviewed-by: Tommie McAfee <tommie@couchbase.com>
Tested-by: Tommie McAfee <tommie@couchbase.com>