Linux Keyrings: don't ignore error code from session keyring creation

Linux Keyrings: don't ignore error code from session keyring creation

Creating a session keyring can fail, for instance if the user's
keyring quotas are reached (number of keys/keyrings or data size).

Instead of ignoring errors, return them so they can be passed back
to the caller.

FIXES 126230

Reviewed-on: http://gerrit.openafs.org/1151
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from 0caf14224a9153bb488be9e52d67892a2c441a5a)

Change-Id: Ibffa5ff33f756c9365b1148448039e668d39fb92
Reviewed-on: http://gerrit.openafs.org/1581
Reviewed-by: Alistair Ferguson <alistair.ferguson@mac.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 0bec77e1f9dfdb7927926953b808603647910cc0)