kovidgoyal@5e645a7 fixes the password file creation, allowing it to be
unlinked, but read_data_from_shared_memory/1 rejects the shared object
if it is not read only, and will break the ssh kitten for all
platforms.
This change removes the read only check, relying only on the file
ownership check.
This fully fixes#5928
Signed-off-by: Loren Schlomer <me@schlomie.com>