MB-11324: disable collect button after click

Change-Id: I9828deaeb95e3e56c787b19b8ddd3267ab9d32e3
Reviewed-on: http://review.couchbase.org/38007
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>