prdb_check: check for continuation entries in owner chains

prdb_check: check for continuation entries in owner chains

Continuation entries may not be in owner chains. Fix the
comments in WalkOwnerChain (which were probably copied from
WalkNextChain) and add a check and error message for
continuation entries found on owner chains.

Reviewed-on: http://gerrit.openafs.org/11751
Reviewed-by: Daria Phoebe Brashear <shadow@your-file-system.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit 3e9e244d1004972f202490faa0375768959f7690)

Change-Id: I8da044e32e6ade0d8d3050ccebf46d1e735e333a
Reviewed-on: http://gerrit.openafs.org/12103
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>