MB-25237: Improve error message that is shown...
MB-25237: Improve error message that is shown...

...when loading of sample buckets fails because certain services
have not been started.

Change-Id: Iaaed77e0e33f78c27a11d9732bad9d16d8db9328
Reviewed-on: http://review.couchbase.org/82224
Well-Formed: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Tested-by: Ajit Yagaty <670a5cadfa9668cb910cc315f6527868cd5ab42a@couchbase.com>
Reviewed-by: Artem Stemkovski <15a0730a27c69f62ab86f2b6c639fca202166c02@couchbase.com>

membase/ns_server,membase/ns_server,membase/ns_server,membase/ns_server,membase/ns_server,membase/ns_server