Allow to select bootstrap providers

Change-Id: I77a3b46f2663788e8eb7f2a63edc690c1f59e2af
Reviewed-on: http://review.couchbase.org/35986
Reviewed-by: Matt Ingenthron <matt@couchbase.com>
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>