viced: Do not try to reuse deleted client

viced: Do not try to reuse deleted client

When h_FindClient_r encounters a deleted client structure, it does not
try to find a different client structure to use. Force it to use a new
client structure by setting client to NULL when it detects a deleted
client.

This arguably reverts part of
4e55e30f5b2c149b350b6d6875793adf722fdc21, but the code paths in
h_FindClient_r are very different now, so that commit is probably not
too relevant.

Change-Id: I8e5004c8a9a3d99919da8df4436e5aa97e338825
Reviewed-on: http://gerrit.openafs.org/4582
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>