CBLT-283:  use: s3://packages.couchbase.com/builds/mobile/${VERSION}

Change-Id: I3f207a3bc5d3aa7a18ef6d0f38984fac1800777d
Reviewed-on: http://review.couchbase.org/36761
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>