viced: Clear all client CPS on FlushCPS

viced: Clear all client CPS on FlushCPS

Currently the fileserver only finds the first applicable 'client'
structure (via h_ID2Client) for a FlushCPS operation, and invalidates
the CPS for it. However, there may be many 'client' structures in
memory for the given viceid, since we may have many connections for
the same user (possibly from different hosts).

So, modify FlushCPS to find all relevant client structures, and
invalidate the CPS calculation on them.

Change-Id: I46532984cc470f41c83fb8c686766e4a4d49edd0
Reviewed-on: http://gerrit.openafs.org/7574
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>