lib, vtysh: Return actual problem further up

lib, vtysh: Return actual problem further up

When we encounter a problem loading a config file
quantify to the end user what has gone wrong,
with a combination of err output as well as
return codes.

Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>
Reviewed-by: Don Slice <dslice@cumulusnetworks.com>
Reviewed-by: Daniel Walton <dwalton@cumulusnetworks.com>
Reviewed-by: Dave Olson <olson@cumulusnetworks.com>