MB-6972:  use double-quotest so `date` will evaluate

Change-Id: Ib2d212b9d2e0700deda1172178af36a086c0c359
MB-6972:  add GPG key location to ssl part of couchbase-server.repo

Change-Id: Iaaea514ef1738d3d0a5449cedc28cdb720edd5ba