Changeset 10877:19a630782b82
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ruby: cleaner ruby tester support

This patch allows the ruby random tester to use ruby ports that may only
support instr or data requests.  This patch is similar to a previous changeset
(8932:1b2c17565ac8) that was unfortunately broken by subsequent changesets.
This current patch implements the support in a more straight-forward way.
The patch also includes better DPRINTFs and generalizes the retry behavior
needed by the ruby tester so that other testers/cpu models can use it as well.