lfs: use the local store method for opening a blob
I noticed that when I cloned without updating and then turned around and pushed
that clone to an lfs server, it was only trying to find the blob in the local
store.
Writes to the dummyremote (file based store) use local.read(), which looks at
both the usercache and local store.
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}