When we get an error return code from userspace (the client-core)
we check to make sure it is a valid code.

This patch maps the whacky return code to -EINVAL instead of
propagating garbage back up the call chain potentially resulting
in a hard-to-find train-wreck.

The client-core doesn't have any business returning whacky return
codes, but if it does, we don't want the kernel to crash as a result.
Signed-off-by: Mike Marshall <hubcap@omnibond.com>