Using cached metadata should not be a silent error

[ecordell]

The notary client being unable to update and re-using cached local metadata instead should not be a silent warning that's only visible with debug logging:

WARN[0002] Error while downloading remote metadata, using cached timestamp - this might not be the latest version available remotely

Depending on what you're doing it may be okay to use the cached metadata, but it probably shouldn't be silent.

[riyazdf]

Agreed - I think the default logging level is fatal.

Generally I'm of the opinion that maybe we should lower notary's default log level to warning or error and adjust the verbose/debug flags appropriately? It could also be a print, which would be a simpler fix though there could be other cases like this one that we want to bubble up.