Fix a reference leak for node devices.

Fix a reference leak for node devices.

There were some major, and some minor bugs having to do with
the reference counting of node devices in daemon/remote.c.

Some functions were completely failing to unreference node devices;
this would lead to many open file descriptors, which would eventually
fail.

The minor bugs were along the same lines, but were in rarely
used error paths.

Signed-off-by: Chris Lalancette <clalance@redhat.com>
Signed-off-by: Matthias Bolte <matthias.bolte@googlemail.com>