Flushing a bucket fails with unexpected error when view indexes are being built

Steps:

1. Create a bucket "data-bucket".
2. Add a million docs to this bucket.
3. Start sync gateway with its json pointing to this bucket.
4. Flush the bucket from the UI once the sync gateway view indexes are being built.

Actual:

Flush fails with " Flush failed with unexpected error. Check server logs for details. " message

In the UI -> Logs, I see:

Flushing "data-bucket" failed with error: 

{error,{prepare_flush_failed,['ns_1@192.168.33.21'],[]}}

Flushing "data-bucket" failed with error: 

{error,{flush_wait_failed,

Expected:

Either the bucket flush should work with the view creation aborted or a busy message should be displayed.

Server logs:

http://supportal.couchbase.com/snapshot/66d21f872c5f6294d5fd40a2fe0f3b74::1