Changes

osmo_io: Propagate segment_cb errors to the read_cb

Previous logic was to drop an entire msgb in the stream and pretend it
can continue working that way, which clearly makes no sense.
Instead, if segment_cb detects some problem (eg. buggy peer sending
corrupted data according to protocol), propagate the issue through
read_cb() so that the app can act on it, ie. most likely close the
connection.

Related: SYS#7842
Change-Id: I572e68df6799b903507229a9beee6fa7d7d6d652