Force schedule snapshot task on bucket creation

Because we de-duplicate the snapshot task scheduling, it
is possible that a
Delete,Create gets re-ordered as Create,Delete because the
first create task was de-duplicated but the actual task runs
before the Delete task

Change-Id: I2d617ff2a63d4a6ff592ee03f883d5a9e75fd588
Reviewed-on: http://review.couchbase.org/36300
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: abhinav dangeti <abhinav@couchbase.com>
Fix race conidtion when deleting vbuckets

There is a race condition where we create, delete, and then create
a vbucket. The problem is that the the first create can finish
after the second create is started. When this happens the code
thinks that the last create has finished even though the vbucket
deletion has not. This can cause items to fail to persist to disk.

Change-Id: I66e6450481acda2250bb7e13f921f3e9d20fbee1
Reviewed-on: http://review.couchbase.org/36254
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>