Provide a "--local" flag to "bin/conduit call" to force in-process execution
Summary:
See PHI1692. Currently, it's hard to get a local profile or "--trace" of some Diffusion API methods, since they always proxy via HTTP -- even if the local node can serve the request.
This always-proxy behavior is intentional (so we always go down the same code path, to limit surprises) but inconvenient when debugging. Allow an operator to connect to a node which can serve a request and issue a `--local` call to force in-process execution.
This makes it straightforward to "--trace" or "--xprofile" the call.
Test Plan: Ran `bin/conduit call ...` with and without `--local` using a Diffusion method on a clustered repository. Without `--local`, saw proxy via HTTP. With `--local`, saw in-process execution.
Differential Revision: https://secure.phabricator.com/D21114