Use cluster type connection for cbc-bucket-flush

Although flush command is accessible for bucket type connections,
cbc-bucket-flush doesn't use provided bucket name to connect to,
therefore it will fail if the bucket name isn't "default".

Change-Id: I4751dbd1acecfeda2f5c819730f8daa4df43f3bb
Reviewed-on: http://review.couchbase.org/28755
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Prefer lcb_assert() to abort()

Change-Id: Ie824d6e75f24876e31a0eeede90a66d3a3380ccd
CCBC-263 Skip unfinished SASL commands

During rebalance, it is possible that the newly added server doesn't
have chance to finish SASL auth before the cluster will push config
update, in this case packet relocator messing cookies.

Change-Id: Ic3fb01b4a39d2e8e68c690c264a2918d631d9602