Merge all returns paths from dispatcher into single path

Merge all returns paths from dispatcher into single path

The dispatcher functions have numerous places where they
return to the caller. This leads to duplicated cleanup
code, often resulting in memory leaks. It makes it harder
to ensure that errors are dispatched before freeing objects,
which may overwrite the original error.

The standard pattern is now

    remoteDispatchXXX(...) {
        int rv = -1;

        ....
        if (XXX < 0)
          goto cleanup;
        ...
        if (XXXX < 0)
          goto cleanup;
        ...

        rv = 0;
    cleanup:
        if (rv < 0)
           remoteDispatchError(rerr);
        ...free all other stuff..
        return rv;
    }

* daemon/remote.c: Centralize all cleanup paths
* daemon/stream.c: s/remoteDispatchConnError/remoteDispatchError/
* daemon/dispatch.c, daemon/dispatch.h: Replace
  remoteDispatchConnError with remoteDispatchError
  removing unused virConnectPtr