viced: Catch GetCellInfo failure

If GetCellInfo returns a non-zero result, catch the error, rather
than just carrying on regardless.

Caught by clang-analyzer

Reviewed-on: http://gerrit.openafs.org/9240
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
(cherry picked from commit 1d1ba5f74102ae703ef657aa19150729edfe6ab2)

Change-Id: I205b32a3e38faeae8e06bad3dc615ba01f0626d8
Reviewed-on: http://gerrit.openafs.org/9533
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>