a5413281e0

Controller scaling was broken by the commit 02772ba2877b9f6d427c6fd760bf19d6334c68a8. Merge.py raises an exception when it tries to scale the default value "controller0" of the `BootstrapNodeResource` parameter. This reverts back to using Fn::Select for specifying the bootstrap host, the rest of the Fn::Select -> get_attr changes are kept. Change-Id: I0cdebf75d4752a35f547d4fbb81545ece3172405
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