ukernel: handle pioctl errors properly in ktc

ukernel: handle pioctl errors properly in ktc

the straight return from call_syscall isn't what we want. munge so
e.g. EDOM handling for ktc_GetToken does the right thing.

Reviewed-on: http://gerrit.openafs.org/5807
Reviewed-by: Derrick Brashear <shadow@dementix.org>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit b06c700ee40ca70ef08259af819e2a6084137457)

Change-Id: I8929615940cb4f025bdd04139399f0ceb82955c9
Reviewed-on: http://gerrit.openafs.org/6084
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>