net: lwm2m: improve return errors from update_attrs()

When any error is returned from update_attrs() in engine_add_observer()
an EINVAL is returned back to the caller.  Let's return whatever error
code was generated in update_attrs() instead.

Also, add handling where previously errors were ignored.

Signed-off-by: Michael Scott <michael@opensourcefoundries.com>
1 file changed