Cache: Use CControl to enumerate Cache instances
Cache: Use CControl to enumerate Cache instances

Run "ccontrol qlist" and parse the output to collect a list of available
Cache instances.  Provide an "INSTANCE" cache entry to choose among the
instances found.  For convenience, prefer instanc CACHEWEB or TRYCACHE
if it exists.  Otherwise just default to the first instance listed.

Change-Id: Ib645ce60528542ade7043bed0dfb6878e6a26cf8

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