MB-11820: Move cbdocloader to bin directory

Since cbdocloader will depend on cbtransfer to upload data, it has
to sit in the same directory as cbtransfer does.

Change-Id: I6f1c02d19d7a357c03b4620c243591e792b9edfe
Reviewed-on: http://review.couchbase.org/40656
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Bin Cui <bin.cui@gmail.com>