os: Mark client as ready to read when closing due to write failure [100863]

This makes sure the server will go look at the client again, notice
that the FD is no longer valid and close the client down.

Bugzilla: https://bugs.freedesktop.org/100863


Signed-off-by: Keith Packard <keithp@keithp.com>
Reviewed-and-Tested-by: Michel Dänzer <michel.daenzer@amd.com>